Chart for 8.75 axle flanges?

I had a similar question bouncing around my head. I have a 69' Cuda 8 3/4. I may upgrade the axles with ones from "John" at "Mopar Maddness" on "Ebay". They would be 5x4.5 to match the 73'-76' discs up front. I can get a cheap 8 1/4 out of a 72' Polara. Could I swap the Polara rear drums and backing plates over to the Cuda rear axle with the aftermarket axles. Or is this a question for John? If this worked, I could also get the rims and other hardware cheap. One stop shopping.