Well we did it, we had to mess around with the mounts a bit and the engine sits a little closer to the firewall (but not in a bad way) but we were able to flush the tranny and get everything together.
The original engine had 178k miles when it threw a rod, couldn't be fixed. I'll post more when we actually get the truck running up to full steam. We need to do a few oil changes, engine flush, and radiator flush before we'll know if all is well...