i think your pedal ratio on that setup is about 6.2:1. that's similar to the one i modified to turn the master 90* behind the dash on my humpback, and that's what the ratio was on it. that should be ok. i'm using a .944[metric 15/16"] minivan master and large GM[impala] front calipers with 12" mopar cop rotors on the front with 12" wilwood rotors and GM metric calipers on the rear. got an adjustable prop valve to get the front/rear bias. rear tires are 33x17w and fronts are tiny 165's. that ought to be fun stopping with that combo.
if you switch and can't get roughly 1000psi, use the calculator that "feets" came up with, or mark wiliams calculator. plug in the pedal ratio, master size and caliper bore. it will give you the psi and leg effort necessary to obtain it. let us know what you come up with.