Looking at original underhood pics. Also, some of these guys have researched the assembly process quite thoroughly, and some have NOS master cylinders. The Firebird m/c was a different style than the A-body. It was fatter and lower, probably for hood clearance.

My master cylinder is actually a natural cast color (which I cleared using satin clear), and I've been meaning to paint it black.


Here's a correct master cylinder on a 69 Bird 400.