Power brake pedal not the hot ticket for manual brakes. The pedal ratio is a lot less. If you can find a manual pedal and a master with a 15/16 piston I will guess you would see around 1200 psi maybe more. 800 psi and discs must get a little exciting in a not so good way. There are some math formulas that you can calc out pressure for a given pedal ratio/pedal input/master piston size.
AndyF would be a good source for that info.
Kevin
Oh it's exciting allright...trying to stop 4100lbs at 125+MPH sure gets interesting. The car should pick up substantially with the new Tq converter so this has me concerned.
Kevin, I've searched and haven't been able to find a manual brake specific brake pedal. Might have to make my own
From what i've reserched so far : the power brake ratio is 5:1 and the manual brake is 6:1. When i converted mine i remember having to redrill the brake pedal arm to align the pushrod to the master...moved it lower which i'm sure had a negative impact on the ratio. The manual master sits lower in the engine bay and uses a different firewall plate....hence the requirement to redrill a new hole for pushrod alignment. I may be at less than 5:1 ...need to disassemble and do some measurements
Using the calculator @ Mark Williams racing i came up with a 6.32:1 pedal ratio requirement for 1200 psi using a 1in bore master and 150lbs of foot pressure on the pedal.
Going backwards, i come up with a ratio of 4:1 to achieve 800 psi with 150lbs of force so that's probably what i currently have.
...need to disassemble and do some measurements 
