Let me tell you how lucky i am, finally did a cam/ head/ converter swap on my truck aaaaand a freakin hail storm comes and destroys it. Insurance totaled it but i bought it back for parts. I am looking at a 2006 ecsb 5.3l/ 60e 2wd with 174k miles. my question is since my original truck has a solid drive train, lq4, 80e, 14b, could i swap my engine and trans in the 06 using my original 03 wiring harness and not have to do all the wiring modifications? would the ecm support the different truck or would it not work? I searched for a bit but didnt come up with much. I was gonna look at newer trucks but i'd rather have my old set up in a new (to me) truck. Thanks in advance

 

03 and 06 are the same. I think the fuel rail may be different. So the swap would be easy

 

The Gas pedal, Tac module, and possibly the Throttle body are different. Either need to use 03-05 or 06-07 classic for the GMT800 trucks

The 03 is probably still a return style fuel setup. The fuel injector table will need to match what ever style fuel system you use.

Can you make everything Work Yes, but you need to use all the correct parts.