Despite the fact that the V8 conversion is probably the most common modification I see on these AD trucks, it is also a total custom job and an absolute exercise in frustration. I've successfully converted mine and I'm STILL having issues.
Most people use a log manifold for the exhaust on each side because that's about all that will fit in the ridiculously narrow space between the framerails. I was dead set on headers. You can try this as a possibility, and I'll tell you the problems I had.
I bought a set of shorty headers (basically block-huggers) off of a stock '86 Corvette. I turned them upside down and wrapped them real good with fiberglass header wrap. I had to take the stock heat shields off them because no way would they fit with those. So with the headers sticking up in the air, I ordered a set of stock-style ball-type flanges and welded them to J-bends. The J-bends had to have custom sections welded on to clear, but basically, they turn back down in the rear corners of the engine bay. I wrapped those too. From there, the exhaust is a conventional dual exhaust.
The main problem I'm having is heat. Let me re-phrase that...HEAT!!! Even though they're all wrapped, I still have a problem with melting wires. I need some better heat isolation, which I'll work on.
Or, here's another thought. Can you get two different types of headers? Check out the swap meets. My Corvette headers were in beautiful shape and were only $5 bucks for the pair. At that price, you can afford to experiment.
