master cylinder

mvh said

No, A-body disc master cylinders were either 15/16" bore or 1-1/32" bore. B-bodies came with 1" bore (also 1-1/32 and 1-1/8), and all these master cylinders are interchangeable, so you could wind up with any of those sizes if you wanted. Note that the pushrods will be different for power and manual, and some may not have the correct piston stop for manual applications.

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My bad (mvh) according to the Manuals you are correct.

My question is what gives??? Same calipers and essentially all is the same including the Booster for PB. The one difference is or may be the frame T/ safety switch, or maybe in 72 it is the frame T/safety switch/proportioning valve.

Attached is a the specs from 1969 first 2 pages and 1972 second 2 pages. Makes little or no sense to me.