BNielsen
I'm Awesome
Find a Treasure Yard Vortec 7.4 vehicle. Grab engine, transmission, computer and harness.
Remove your engine and transmission, install Treasure yard parts. Remove your ECM and harness, install Treasure Yard parts.
There's probably more to it than just that--I have no idea how the instrument cluster, ABS, TPMS, and cruise control will appreciate being switched from one ECM to another.
If you can't do this yourself, you might as well pass. Paying a shop to configure all this stuff will cost arms and legs, and if it doesn't run "PERFECTLY" you're going to see a decrease in the resale value because it's a FrankenTruck.
I still say that if you're towing a bigass trailer, you might as well get an '05--'06 Duramax and be done with it. Everything else that involves modifying the 454 or slapping in a 502 or Cummins or whatever is going to be a tuning nightmare with zippity-doo-dah for resale value.
@andy396 could chime in with a little more detail on the difficulty level of doing an L29 swap. But he used the stock harness and integrated it with the stock harness. I know that I probably wouldn't ever do it myself unless it was an absolute gem of a 95 I'd want to upgrade.
Even with the 05-06 (LLY/LBZ) Duramax you'll run into troubles, they were notorious for head gasket issues, as well as a few cooling issues that really didn't get ironed out until the later LBZ and LMM engines.
Man, going through this thread makes me overthink things.