Which master cylinder bore size to use for power disc Kelsey/Hayes

if the system never worked right, you'd probably be better off systematically checking and eliminating each component from the list of offenders. dana has a great checklist there in the previous post.

the MC is a good start, and maybe that fixes it from the jump. but it would behoove you to take a deep dive into the system in the case of that just being band-aid for other underlying issues.

at least with power the size of the MC bore is a secondary concern.