Give me a brake

I bought a 71 Demon last weekend it was an orginal 6 cyl car, it now has a 360 cu in it and a V8 K member with power disc brakes, also has a V8 8 3/4 rear with drums in it
When i put the brakes on the car stands on its nose it brakes straight but its like the fronts are working to good. And a few times its like the pedal wont release any ideas?????????
Thanks Ray