I have a 1999 Suburban C2500 with the 454 big block and the 4L80E trans, my question is this. Can I directly swap out the 454 with a 350 and keep the 4L80E trans? I'm hoping to do a direct swap with as little "rigging" or changing as possible. If so, which 350 should I use? I want to stay with fuel injection.

dj

350 and 454 has the same transmission bolt pattern.
But you will need a lot of VCM/PCM and wiring swapping.
After swapping you will need insurance and license and title changes to stay legal.

Is it reasonable to think I may be able to pickup the complete engine wiring harness, VCM/PCM from a bone yard, or should I not do that? If not where would you suggest I get these items, most dealer don't want to fool with changing parts and computers around? The 454 is more engine then I need and the fuel is not helping feeding this beast.

Yes make the local bone yard you best freind.
Dealer stuff to change over could run 3-4 grand plus engine.
Good Luck
MT