Alright since you say you'll do it anyway, you're going to need to find a wrecked 5.3 V8 SWB TB 4WD. Has to be exactly that. An SS wont work because the xfer case is different so the wiring is different too. Remove the WHOLE wiring harness, cluster, radio, HVAC controls, 4WD switch, basically pull the whole interior from the wrecked V8 TB and move it into your Bravada. Then get the engine/trans/new driveshaft swapped in (take the diff from the wrecked V8 TB, dont know if the fullsize ones mount differently or not) and get everything bolted up. Need new fans (go efans for a fullsize, wire them like a fullsize) at the minimum, most accessories should work from the fullsize engine (but if not have to retrofit I6 and/or TB V8 components).
I know you want this to work man, and if you do Ill help you with as much info as I can but this swap is going to be a TON different, much harder, and way more expensive than your LS6 into a 240sx swap. All the modern day electronics have to talk to each other perfectly otherwise you're going to spend weeks if not months tracking down little electrical issues.