Hey guys ive been looking through many forums including this one for help on a c15 96+ carb swap with 4l60e. There was two builds on different forums, but they were not clear on how they did the swap. I managed to get my 97 wired up and it was super easy. You can keep all the fuses and fuel relay thats originaly on the truck. This was my first time doing this on this later model truck but it worked like a charm. Basicaly what you need to do is send crank signal to the original pcm so you wire the 5.3 to the 4.3 pcm and Wala.. you have fuel pressure ant ignition key. I used 1" set back plates took off the v6 4.3 motor mounts and installed sbc 350 truck mounts. Mounted right up no problem, I had plenty of space between the trans and firewall. Space enough were a I could put a a/t bolt through the top of engine bay. Original heater hoses pugged right in, so did the brake booster vaccum hose. Here are some pics...