Funny you should ask, I joined here just now to ask that very same question as I just picked up an E Body 8.75 dirt cheap complete drum to drum with 489 carrier and I had been thinking of cutting it down and getting aftermarket axles.
Where are you located? I have an 'A' body housing that I'm willing to sell. E body rears are about as hard to come across as cheap E bodies are but I usually install B body rear into the E's anyways.