96 Ecsb k1500 5.3 swap help

[lsx96z71]

Well this is my first post and I guess I should introduce myself. I'm Dakota. Gm service tech for 7 yrs.

Anyway, my 96 5.7 spun #4 rod bearing, and I have a 5.3 laying in the shop that I would like to swap in. I've done quite a bit of research but still have a few questions that I hope you guys can help me with.
I'm not sure what year the engine is. But I believe it came from a van. It had a bracket bolted to the pass head that trucks and tahoes don't have, and the brake booster line had a plug instead of a nipple. It is drive by cable and it has an egr valve.
For a harness an ECM, what I understand is that I need a harness from a 99-02 dbc 5.3 gm vehicle and a 12200411 ECM. I plan to modify the harness myself. Do I keep my old black box? What do I need to keep out if my old harness to make all gauges work?
I plan to run ac. Can I run the express 2500 5.3 compressor? It seems to be small enough to fit in the factory ls location.
I'm using my 96 4l60e. It has been heavily upgraded. I know I need the 6.0/4l80 crank spacer. Which flex plate do I use, The 5.7 or 5.3?
I have the 1" setback mount adapters.

[Lextech]

Nelson Performance (The owner of this forum) can set you up with a harness or you can modify your stock 97 harness to run the Gen3 engine. The Gen3 A/C compressor will fit in its stock location with a BIG notch taken out of the frame of your 97. You can also use your 97 A/C compressor and lines in their stock 97 location with an adapter bracket kit. There is NO need to run 2 PCMs. The 12200411 PCM will run everything on your truck just fine by itself.

Jeff

[lsx96z71]

It's a 96, but it's the same. I am modifying a harness out if a 2000 silverado, extending some wires, shortening some wires and running everything behind the intake to the passenger side. If anyone can hook me up with a how to for hooking it into the factory harness for gauges and what not. And which flex plate do I use?

[Blasphemy]

It's a 96, but it's the same. I am modifying a harness out if a 2000 silverado, extending some wires, shortening some wires and running everything behind the intake to the passenger side. If anyone can hook me up with a how to for hooking it into the factory harness for gauges and what not. And which flex plate do I use?

What Jeff meant to say was, buy his custom bracket kit (I'm a proud owner of one) to keep your A/C and Alternator in their stock locations. All you have to do move around a little wiring for both and you're good. From my understanding, you can just buy the spacer/bolt kit on summit or jegs and run the flexplate you have http://www.summitracing.com/parts/tfs-30675700 also a member on here named capricefrk013 has one for sale, maybe it's still in his signature. His thread is the one that says 6.0 into OBS, it's an informative one, you should read it.