Call NPD. They might have them. I know Summit has a good variety. Forget about the parts store. The only thing I get from them is oil.

 

It might work out well for you, Urban has updated to Wilwood calipers which might make a difference.

I didn't realize that the stock displacement ratio was insufficient when I made my post.

 

I do not pretend to understand all the issues involved, but from what I have heard, it is an issue of matching fluid volume for the particular caliper or drum used. A bigger bore in the MC moves more fluid. This is a good thing if you are running a huge caliper with big pistons. Sometimes you don't know until you try. I thought my Wilwood 4 piston calipers would need more volume, but they did not really need anymore than the Granada calipers.

 

It is all about mechanical advantage, or if you will leverage... a smaller bore m/c will make for a comparatively longer effective stroke and less pedal effort.

Certainly when changing the volume of the calipers, this can mean that changing the volume of the m/c is a good idea, and it can be done to the benefit of personal preference within reason.

IDK, I was just trying to give the "safe answer" assuming that a proper stock m/c would work right with the right stock brakes, (and there are tons of factory options for Mustangs).... I always thought that stock pedals felt pretty good for the most part, and this is what I have gauged my mix and match installs against.

Jim's manual Mustang brakes (with Wilwood fronts and SBBC rears) like yours have a long steady stroke that I liked once I got used to it, my Lincoln with power drum brakes has a pedal that is a bit harder than it was stock, still great once I got used to it. IMO so long as the brakes will lock before the pedal hits the floor, and the pedal is not too damn hard everything is cool.

I think the o/p's issues were a result of the wrong pushrod more than the wrong diameter cylinder.

 

Good discussion;
Other points to consider include things like bigger wheels, wider tires, drum to disk conversions, etc..
All these conspire to change the stock parts applicability to a no longer stock configuration.
My brakes will not lock up at all, not that I want flat spots on my tires mind you. But I would like to stop quicker than I do now. The smaller piston may give me more psi at the sacrifice of needing a longer stroke, but I think I have plenty of that to spare.