8.75 Brake ???

The difference is in the axles!!!!

A body SBP axles use a different offset than LBP axles to run the narrower 10x1-3/4" brakes. So, if your new axles use the original SBP offset, you just need to drill your drums for the larger bolt pattern.

BUT, if your axles use the normal LBP offset, then you MUST use the 10x2.5" backing plates, drums, hardware, etc.

Find out which length/offset your axles have. I believe that Mosers off the shelf stuff is the original A body length and offset, but other manufacturers use the LBP length.

Personally, I would get axles set up with the LBP offset. 10 1-3/4" drums are getting harder to find, and you every time you need new drums they'd have to be drilled for the LBP. If you get axles intended to use 10x2.5" brakes, you just buy off the shelf parts that are easily available.

And I wouldn't buy any of those 10x2.5" brake kits new. The 10x2.5" brakes came on all kinds of Mopars all the way up to the 90's, so they're easy to source at the wrecking yard. Or eBay, they'll cost more than the wrecking yard but should cost a whole lot less than $350.