Up powering an M43, engine swap, engine+ drivetrain, or engine, drivetrain, and frame

[minnhawk]

I have a 1953 M43. I would like to put a bigger engine and disc brakes in it for long-distrance highway driving. I have a donor 2006 GMC 2500 stretch cab pickup w/ 6.0 vortec& 4L80E auto trans.
I have completed the restoration on the M43 & repainted with crosses and correct numbers, etc.

1. Should I start by swapping the engine and transmission in? 6.0 swaps appear to fit (Petersen's 4 Wheel Drive , March 1, by Fred Williams "1965 Dodge M37 The Dumpster: Part one) and youtube author "Itchy Old Fart"

2. I would also like to swap the M43 rear end with the corporate 14 bolt GMC rear end with rear disc brakes. I would also use the master cylinder power brake set up from the GMC. (see previous cites)

3. I would also like to put disc brakes and power steering kits on the front axle.

OR

Should I measure up the GMC frame against the M43 frame and do a complete frame/powertrain/axle swap? I believe the GMC frame would have to be shortened. Someone mentioned that alternative on an old post on the G741 forum.

The more I ponder it, the more sense it makes to just swap the frames out. Either way, it is a lot of work, but the frame swap would actually be less expensive because I wouldn't have to buy brake and steering kits, engine mounts, re-perching the rear axle and so on.


WHAT DO YOU THINK? I need advice for my winter project.

 

[exhogflyer]

Don't do it ! Sacrilege to hack up a piece of history because you want to drive an old ambulance on the highway.
Sell it and buy yourself a new Tahoe, paint crosses on it if you want, **** I'll even help you!

 

[nattieleather]

It's your truck if you want to do an engine swap and paint it hot pink I say go for it....M43s are not that rare that you need to save every last one of them IMHO. But to answer your question. The frame swap may be easier to do than axle and motor/trans swap. To frame swap you will have some work getting the wheel base the same, getting all the mounting points figuring where things will fit, but I think in the long run it will be less work and less $$$ to do the frame swap. If you do the drive train swap on the existing frame then you have the problems of getting the front axle mounted because of the dodge frame moves in at the engine compartment (it's not a straight H or ladder frame but more of an A frame). Engine mounts, trans mounts, changing the axle perches on the rear axle etc. I've been repowering and reaxle a M37 for some time and in hind sight I would have been better to do a complete frame swap. My truck might even been driving by now if I had.

 

[thmpr]

Check out the thread Canadian M152 camper/bugout mods. Similar body to M43. The whole frame swap will be pretty intense. I did that to my 1952 Willys pickup - mounted the body to a long 1994 K2500 3/4 ton chassis/running gear. Had to shorten frame by 6 feet overall (3 feet in the middle and about 2.5 feet off the back) and move engine/trans back 1 foot to maintain the correct look of a forward front axle. The M43 has the same issue - the engine resides behind the front axle - not above it. Will have to move the whole engine/trans back to get the correct look.

Like you, need a reliable highway capable resto/mod. Installing different running gear in the M152, but keeping stock frame. Yes you have to grind axle housings smooth and install new perches, new engine/trans, but I think would be simpler. The M43 frame is beefy.
Glenn

 

[minnhawk]

Don't do it ! Sacrilege to hack up a piece of history because you want to drive an old ambulance on the highway.
Sell it and buy yourself a new Tahoe, paint crosses on it if you want, **** I'll even help you!

Ah, the first reply is from one of the high priests of the Pentecostal HMV Church. (just kidding, but you used the word sacrilege) It's ok - I have faithfully (painfully) restored a 1945 DUKW, a 1942 WC-56, and am still working on two GPWs. My dues have been paid to the hobby in time, money, and effort.

Now I want a pseudo HMV that can get me across the country and back to participate in MVPA convoys. An HMV that looks the part but can also get me to York, PA and back from San Franscisco and places like that. I've towed both the WC-56 and the M-43 cross-country to participate in convoys, but it has been difficult to find someone who is willing to drive the towing rig back home and then go out and get me when the convoy is over.

The M-43 has faithful early Korean OD paint and correct markings for the 3rd Medical Battalion, 3rd Infantry Division in Korea. Her crosses are correct as are the medical markings for the US Army Medical Service. It's pretty. It was one of 5 ambulances on the '19 Lincoln Highway Convoy.

 

[minnhawk]

T

It's your truck if you want to do an engine swap and paint it hot pink I say go for it....M43s are not that rare that you need to save every last one of them IMHO. But to answer your question. The frame swap may be easier to do than axle and motor/trans swap. To frame swap you will have some work getting the wheel base the same, getting all the mounting points figuring where things will fit, but I think in the long run it will be less work and less $$$ to do the frame swap. If you do the drive train swap on the existing frame then you have the problems of getting the front axle mounted because of the dodge frame moves in at the engine compartment (it's not a straight H or ladder frame but more of an A frame). Engine mounts, trans mounts, changing the axle perches on the rear axle etc. I've been repowering and reaxle a M37 for some time and in hind sight I would have been better to do a complete frame swap. My truck might even been driving by now if I had.

Thanks for your reply. I studied several other LS 6.0 conversions done on M37/43s available on youTube and such, and I have pretty much come to the same conclusion as you suggest. Both methods are a major headache, but trying to refit the M37/43 frame with a modern drivetrain (even just keeping the rear
axle) would be a much bigger headache than the other way around. I think we'll start after the New Year by stripping the pickup body off, getting the 2500 frame into the shop, and start measuring it up alongside the M43.

 

[minnhawk]

Check out the thread Canadian M152 camper/bugout mods. Similar body to M43. The whole frame swap will be pretty intense. I did that to my 1952 Willys pickup - mounted the body to a long 1994 K2500 3/4 ton chassis/running gear. Had to shorten frame by 6 feet overall (3 feet in the middle and about 2.5 feet off the back) and move engine/trans back 1 foot to maintain the correct look of a forward front axle. The M43 has the same issue - the engine resides behind the front axle - not above it. Will have to move the whole engine/trans back to get the correct look.

Like you, need a reliable highway capable resto/mod. Installing different running gear in the M152, but keeping stock frame. Yes you have to grind axle housings smooth and install new perches, new engine/trans, but I think would be simpler. The M43 frame is beefy.
Glenn

Thanks for your reply. I'm leaning heavily toward swapping the body of the M43 onto the GMC 2500's frame. If we can't get the measurements to come out,
I'll look at going the other way into the M43.

 

[minnhawk]

Well, over the winter we "did the deed" and swapped out the old M43 frame. I rounded up the necessary parts, donor truck, wiring harness, shift kit and so on. I had two knowlegable mechanic friends do the dirty work during the slow snowy months. It came out pretty dang good, drives well, and stops excellently. Really weird driving the M43 Frankenstein for the first time. Much quieter engine and transmission, auto transmission, power steering, 4 way disc brakes. I was up to 60mph pretty quick. Still a lot to do, but I would say the transplant was a roaring success. The only body cuts were made underneath on the stretcher storage box--not enough clearance for the GMC 2500 frame. Also lost the GMC overload spring pack, but no biggie. Rides very well.

I still need to tie the two bumperettes down in the rear with a 6" c-channel, change out the NDTs and GMC wheels for bigger radial off-road/highway tires, and get some electrical items finished. No air conditioning but will have a heater box and blower installed in the cab. Left the two batteries under the passenger seat but they are now set up in parallel to help run the camper accessories being installed. Plenty left to do.

We cut the frame down 22" and ordered a custom rear drive shaft. Grafted the original steering wheel onto the GMC power steering unit.

I will use this truck as a camper when attending HMV events and participating in MVPA Convoys.