Let us know what you find out when you talk about fab'ing up some rims (especially if you can share photos, dimensions, prices, etc for inclusion on my website).
Most likely your brakes will be ok once they get wet again, but...
The original setup works well when the shoes are properly adjusted and everything else is working properly... Of course, since you are talking about a design that it fairly old compared to a lot of other vehicles that are on the road these days, you may not feel real comfortable driving a truck with the stock setup in any appreciable amount of traffic... Folks who keep the driveline stock, run it in parades/shows/convoys, live in rural areas ect. find that the stock system performs quite well...
A good "first upgrade" is to convert over to a two circuit master cylinder. That way, if something happens to the system you at least have some braking whereas the original single circuit master will loose it all if something happens to the hydraulics.
A much better upgrade, especially if you have a repowered truck or have to deal with urban traffic (that jumps in front of you as you slow down to approach a red light for instance) is to install front disc brakes using the kit from Ray Suiter at Helitool (
http://www.uglytruckling.com). I find that just having the front discs with the stock rear drums is sufficient to stop my M37 when loaded and pulling a loaded M101 trailer when I am doing 75mph, however, the same kit may be used to install disc brakes on the rear as well in order to provide four wheel discs..
The disc brake kit works well with the stock mc, but if you are going to the effort and expense to install it, go ahead and do the master cylinder conversion and have the stopping ability of the discs with the piece of mind that the dual circuit mc provides.
Info on both the disc brake conversion and the mc upgrade is on the
http://www.uglytruckling.com website where Ray has posted his instalation instruction and parts numbers. Keep in mind that the measurements for the location of the holes to be drilled for installation of the MC lines is incorrect on Ray's site and that he has yet to correct the page, better to test fit then drill when you install anyway...
The MC that Ray suggests (and that I and other folks use) is used on 1980 Chevy C30 1 ton trucks, CarQuest20-1584, Bendix 1584. You don't need it, but if it makes you feel better to instal a seperate proportioning valve, Summitt has one: SUM G 3905
