You want around 1200lbs at the caliper with manual brakes; 750psi line pressure with a 15/16"bore MC is'nt enough. Been there, done that.
TO get line pressures up, ensure your pedal ratio is around 6:1 plus and use a 7/8" bore MC . With 7/8"bore I had just on 1000 psi measured at the caliper with a hard push on the pedal. Car is 3500 lbs with me in it.
I ended up having to use a 3/4" bore MC on my combo that put out just over 1200 psi. Pedal cleared the floor at full push but not by much.