If I source an 8.75 out of C, E, Truck or Van to have narrowed for a 64, using the large bolt pattern and 11" brakes, does the housing go to the 66-72 width [52.625] or a different length?
My 2 cents. Get the wheels you plan to run and measure for overall length. No mistakes that way.
If you re asking about a factory a-body overall width using B body style BBP brakes, the housing flange to flange should be right at 52.07" going from memory
That should get you the 57.125 overall length with brakes installed
Dr Diff has a axle width/length calculator on his site IIRC