Okay try this one to start.
http://members.fortunecity.com/bubbajoexx/The Caddy motors are 4.1 (bad) 4.5 or 4.9 liters from FWD cars. The Deville, I believe has the least complicated computer swap. Late models have major probs (OBD II cars)
You can add a carb or use the FI with a custom chip. You do need to do some computer fooling and wiring mods.
With the 4 speed, you'll need to source/make a flywheel. Yes the actual engine bolts up to the trannies we have.
PBJ (sold me my car) has done one and is a member here. You can email him for info and I'm sure he'll aim you in the right direction.