Great looking chassis work by the way!!!

I'd guess the master cylinder you have installed now is a 3/4" and 7/8" stepped cylinder??? Should be a good size... I think I'd get the system bled, then check front and rear brake pressure with a gauge and see where it's at. Putting a proportioning valve in the rear line is an excellent way to fine tune the rear pressure and establish a good ration of front to rear pressure..... Sounds to me like you are on the right track for a good brake system.....