Addapter wont work without machining, you can use the 4l80e 4x4 spacer, it has the same bolt patern but the foot that mounts to the crossmember is 4.25 inches shorter than the th400 spacer. I built a bracket between trans and crossmember. I had a two wheel drive 4l80e that I converted to 4x4. you only need to change the output shaft and tail piece. Tail piece bolts on externally, outputshaft change requires rebuild. looks like you have already accomplished this. I bought my output shaft and rear tail piece from 'AOK used transmision parts in houston tx (old bammel rd) for $45 you can find them on the internet if you need the tail piece, it is probably cheaper than a machine shop.
I installed my 4l80e without trans jack, IF you install it like the tm says, you dont have to worry about tearing up the seals in the torque converter. Put the torque converter on the trans, bolt the trans to the engine, bolt the torque converter to the flywheel. If you install the torque converter on the flywheel then you need a trans jack in order to line things up propperly an not tear things up. By doing it like the TM, you can muscle it into place, there are allignment pins on the engine. I used a 4 wheel dolly, wood blocks and two small jacks. I rolled the trans under the truck on the dolly, and with blocks and jacks slowly jacked and blocked it up the the hieght i needed then rolled it into possition, a little bit of muscle to get it alligned and ratchet with 4 extensions and a swivel head let me put the bolts in.
hardest part was actually stabbing the dipstick tube. the tube needs a little bit of custom bending and the anchor bracket for the tube will not reach the top bolt hole so it is loose at this time until i get the extension bracket built. It does not move very much at this time because there is no room for it to move but I worry that it may work its way up out of the hole it goes in. I am working on a post of my install. use the tube from your doner if you can.
Other things you have to do: make extension bracket for shifter, extend shift rod, move crossmember back and get your back shaft shortened and your front shaft lengthened.
I installed my 4l80e last week and I am currently installing the Fast tci controller. I still have to get something for a tach signal and also figure out how the throtle position sensor and wiring will be accomplished. after installation, I found the 4l80e to be about 1.5 inches longer than the th400. My driveshafts are supposed to be finished tomorrow.
I will post my entire build with pics as soon as it is finished.
Rich