4.3-5.3 swap

[sr53]

Has anyone swapped a 5.3 LS into a 2007 new body style 4.3 truck?

Will the existing wiring harness work? Can the computer be programed for the 5.3?

Thanks in advance 

[CamGTP]

It can be done.

You need the V8 wiring harness and fuse block for sure. The 4.3 harness is missing lots of stuff well because it's missing 2 cylinders. The computer can be programmed with a GM type tool with a VIN that could work for the swap. Don't expect a dealership to help you any here unless you know someone that knows exactly what you are doing there. You'll likely want to stick with a 2007 operating system so it jives with the rest of the truck.