do you have a PROPORTIONING valve on your brakes? no matter what, like R Pope said you still need to have a PROPORTIONING valve and a rear residual valve anyway. if you have your brakes set up right it dont make no dif. where the mastercylinder is you, should be able to get brakes on it . thats a lot of work changing that over and i think you might have the same problem. JMO

you dont need the PROPORTIONING valve to bleed you brakes out, but if you dont have one you'll be doing it all over again.
are you sure the residual valves are on your car(i think they want work but one way, or they can be put on backwards) if you dont have one on the rear you want never have a good pedal.