wilwood master cylinder question

I use a 15/16" master cylinder on my Challenger which also has 11.75" front disks and 11x2.5" rear drums. Works great! Dr. Diff sells aluminum master cylinders converted to 15/16" for manual brake pushrods.

If you want to go Wilwood I would go 7/8" or 1", the 7/8" will have a little more travel in the pedal but will give a higher line pressure, the 1" will have a higher pedal but slightly less line pressure. Either would fine, just depends on your preference for pedal feel really. I wouldn't use the 1 1/8", the pedal will be high with a short travel so the brakes will be harder to modulate.