7 1/4 rear brake question

In Canada, research shows that all 73up, V8,cars were 5 on 4.5, and all were disc front/ 10inch drum rear.Can't say about slantys, but rumor has it by 74 the Canadian slantys were this way too.The vin tag may be of help. But if it was born with all drums and sbp, then the 9inchers would have been standard.

Your post is rambling and it's possible to decipher it a couple of different ways.
The axles that went to the machine shop were out of what? The original rear with 10"brakes? or the current rear with 9"brakes? Are both rears 7.25ers? Or is the original rear an 8.25? as far as I know, all 8.25ers were lbp and 10"ers. So you see how confusing this can get.
If both rears are 7.25ers then the bearings are the same.The 7.25ers were available in both bps and both brake sizes
And then theres the late bunch, with the funny looking covers......
This can all be solved relatively simply, by measuring the housing that the axles came out of.