What headers will fit???

I think you've got too many different aftermarket parts playing together. Why did you need Schumacher conversion mounts? The Qa1 k-frame should be set up for a V8 yes?

And the distributor shouldn't be in any danger of hitting the wiper motor if the engine is in the right spot. I mean, there isn't a ton of room there but you shouldn't have to worry about the engine mounts causing those two to interfere.

None of the brands of A-body headers fit every car perfectly. Some fit better than others, and some cars have better luck than others do, production tolerance and all. But since you've had issues with multiple brands and styles of headers, I'm inclined to think your engine isn't located correctly.