If I understand what your situation is correctly you have a PU tranny with a bolt on U Joint and no slip joint. This setup requires a 2 piece drive shaft with a slip joint where the the 2 drive shafts join.

As you have to have a slip joint somewhere (no you can't let the springs do the work something will break in a very ugly manner)and you want to run a 1 piece drive shaft so you need a slip joint on the tranny.

Unless you want to disasemble the tranny you have and change the output shaft to 1 that is designed for a slip joint (yolk), you need another tranny that is desinged for the slip joint.

The TH 350/400 came with different legnth tailhousings for different applications. I believe at least part of the reason for this was to help keep the drive shafts short in an effort to reduce vibration. Any of these set up for a slip joint will work. The amount of in and out movement of the yolk is really very short (usually well under an inch).

The main reason you need to pull the yolk out 1-1 1/2" is so you can push it in that amount for the rear U Joint to clear the rear end yolk to remove the drive shaft. Of course pulled out much more than that runs the risk of not full engaging the output splines and tail shaft bushing.

Basically find a tranny set up for a slip yolk and the yolk that goes with it and build your drive shaft.