I drive a swapped 04 Base Model GT, so I've got a little insight here.
Engine: Top swap or L32 swap, don't bother with an L67. I'm running an 04 GTP L32.
Wiring / PCM: It's possible to run with the wiring from your L26, but I don't recommend it. Swap out the engine harness with one from a GTP, and run a GTP base PCM calibration. Depending on your Transmission, you will HAVE to change the PCM programming to match the gears in the trans. This will also require swapping out your ABS module with one from a GTP for TCS to work properly, but that's real easy and pretty cheap. That's the setup I'm running. (Note, a CompG harness / PCM / ABS Module will NOT work without more changes.)
Transmission: You can run any trans with some work.
L26 Trans: 3.05 Gears, non HD Diff, but no other changes required to the car.
L32 Trans: 2.96 Gears, HD Diff, Need new CV Shaft on the passenger side.
L32 CompG Trans: 3.29 Gears, HD Diff, Beefyer first gear Band, a few other upgrades... Need new CV Shaft on the passenger side, Need to replace with Channel Plate / Valve Body / 4th Gear Clutch with GTP parts - This is what I'm running.
As for a donor, find a Running but Wrecked GTP or CompG and have all the parts you need, plus lots of spares. That's the route I went.
-Rob
