i currently have a 03 5.3L ecu and harness and dbw pedal assembly and TB all out of the same truck. for ease of routing the harness in the engine bay and connecting my injectors and not using the adapter plugs, and running a NW 102TB since theyre 8 pin and the truck harnesses are 6 pin can i run a 04 gto harness thats dbw on my 5.3 truck ecu and still have all the pedal assembly and dbw work correctly? (reason i ask is my truck ecu is already licensed with hp tuners)

 

You can.
As long as the PCM has the correct OS for DBW and proper pedal-TAC-TB it will work.
You need to check all the wiring, everything must match the truck diagram.

Get the truck and 04 GTo diagrams, using both you need to make everything match for the 03 truck PCM

 

i ended up getting ordering a harness today from speed scene wiring and an 01 vette ecu thats dbw, sending them my pedal and pedal tac and theyre going to get it all working properly and send it all back