2000 Silverado v6 to lq4 and 4l80 got a few questions

[1badblazer]

I'm gonna go ahead and say I"m just getting started with these engines, I've only delt with carbed small blocks so far. So please bare with me. I am looking at an 06 2wd 2500hd that is wrecked. I am wanting to put the engine ( lq4) and trans(4l80e) in my 2000 Silverado which is 4.3 powered now. My biggest question at the moment is am I going to be able to use the engine wiring harness from the 06 and just change to a DBC TB or am I going to have to get one from a 2000 v8 truck? I know I have to do some wiring for the trans to work if I use a engine harness from a 1/2 ton truck that had 4l60 thats why Im wondering if I can use the harness from the 06 since it already has the plugs for the trans? Are the plugs on my ecm and the 06 the same or different? Thanks in advance and sorry if these are dumb questions

[PitchBlackC3]

The 2006 PCM will have green and blue plugs, your 2000 will have blue and red.
You can use the 2006 harness and PCM, but it won't play nice with your 2000 BCM and HVAC.
The best thing would be to use a 99-02 LQ4/4L80e harness, but you can make the 2006 stuff work.

[1badblazer]

Ok, I will be looking for a 99-02 harness. I've seen a few but they were from 4x4 trucks would I be able to use one from a 4x4 or will it have to be from a 2wd. Thanks

[1badblazer]

Also what kind of issues am I going to run into with the fuel lines? Is the 06 return-less or does it have a return like my 4.3?

[PitchBlackC3]

A 4x4 harness will work, there isn't much difference.
06 is returnless, get a 99-03 fuel rail, or use a corvette filter/regulator.

[1badblazer]

OK I guess I will be looking out for an fuel rail also.