2006 Silverado 4.3 to 5.3 swap questions.

Alright I will apologize in advance, I know this info is probably out there somewhere but I have been looking for the past few days and I am just running out of time for answers to my questions, so I appreciate any info.

I bought a 2006 RCSB auto V6 with the intention of swapping in a 5.3 V8 I already have from another project. I plan on adding some performance parts (turbo, cam, injectors, 4l80, ect) later on, but right now I just want to get the swap done, then later after I have gathered parts Ill tear back into it.

I am not sure what year engine I have, but it is a 5.3 with a drive by cable TB. I know it is not ideal, as the 06s had a drive by wire setup, but how hard will it be to make all this work like a factory-ish truck? I have seen its easiest to have the same year engine and harness that match the year of the donor truck, but with the TB differences I have, should I change the TB or leave it DBC? Will the rest of the connections be the same or will I need to butcher a 06 harness. I don't mind changing pinouts, but I would rather not get into cutting and splicing harnesses.

I know I will need to retune the ECM I have, and just planned on buying HP Tuners and doing it myself, as Ill need that later anyway. So here is a list of the parts I have seen I will need...

5.3 engine with all accessories
06 5.3 motor mounts
06 5.3/4l60 engine and trans harness
Retuned ECM

Also, I plan on swapping in a 4l80e, would it make things a little easier to just do that now? I want to run a full manual VB with pistol grip shifter, and I do have a 4l80 wiring pigtail laying around... Been looking at Transgos HD3 kit, any opinions/experience on that? The ECM I have is programmed for standalone right now with a "manual" trans. Would I be able to get a auto trans program back in the ECM with HP Tuners if I keep the 4l60 and run it as if it was stock?

You can just swap out the throttle body and save yourself a good headache by not chopping harnesses and going to drive by cable.

If you are going to do something like an 80e swap. Go ahead and do it now while you have everything apart. There are guys here that make 80e cross members, you can get your drive shaft shortened, have it repinned, and ready to go.

I had a lightly built 80e put in behind my cammed/turbo 5.3 making 554/557 and that trans was a beast and never had any issues.