says it is
1-1/8" Bore Dual Reservoir Master Cylinder

problem is this is a gm master cylinder. not sure on the interchange to get a 1 inch bore.
searches show some aftermarket stuff that might work. but I want to steer clear of that if I can.

I decided to pick up the corvette booster and master combo from autozone. So I don't have to go out again, if I find it is the problem.
if it isn't I will just return it instead.

I would really like to find a more "factory" solution but not sure it is out there with how cobbled together this is.

I did mention it the other day, just got around to playing with it last weekend.