I started with a 2002 Silverado with the V6, drive by cable.
Bought an 03 LQ9 complete with everything including harness, PCM, pedal, TAC module.
Found out that the wiring for the starter circuit, possibly more is different from 2002-2003, so I bought a 2002 harness and a DBC throttle body, intending to keep the DBC.
2002 harness I bought is from an Escalade, which I found out when I was laying the harness out and taping names to everything - its a drive by wire harness.

The 2002 harness has a 2 pin and a 6 pin connector, verified here https://lt1swap.com/identify_vortec_engine.htm
They are tough to track down it seems, but I've found some used/NOS/aftermarket stuff online anywhere from $200-$400

The 2003 DBW TB that came with the LQ9 has a different, single plug connector, 6 pin.

Now, before I buy the 2002 DBW 2 connector TB, I was reading that even if I did that, there's a chance I cant use my DBW TAC and Pedal from the 2003 as the 2002 is different:
X-Link Throttle Adapter Module"What about the 2002 and 2007 electronic throttle control trucks?

The 2002 trucks use a different throttle body, TAC module, Pedal Assembly and PCM calibration. A straight adapter harness is reportedly all that is required for the LS2 90mm swap in this application."

So, ok. it sounds like I need either
1) a new harness that's DBC for 2002 V8
2) new throttle body to keep DBW harness, new pedal and new tac from 2002 dbw truck

Doing a tbss intake and TB doesn't seem to help either, as I'd still need to sort out the harness issue - the Xlink cable resolves one of the connectors but what about the other side connector? - and choose a DBC TB.

Any thoughts?

 

Yeah doing more digging the TAC I have is part number 12573059 and I need 12574221 if I were to keep DBW.