My understanding is that later C4s came with slightly larger bore to increase the displacement. Pretty sure this happened before 1990 so all ZR1s has the same bore. Another change may have been when ASR was introduced.
I considered C5 master cylinder with a larger bore when I changed my brake caliper and rotors to Wilwood 6 pistons front and 4 pistons on the rear. However, input and output ports on the master was opposite side and dropped the idea. My 94 despite larger calipers works fine with OEM.
If your concern is low quality rebuild, I suggest checking out Davis Corvette. I boght a new brake master from them 3-4 years ago and looked to be OEM.
https://corvetteparts.com/catalog/Da...aster+cylinder