A residual vlave in the front will keep the brakes applied and not release...not a good idea! Have you all checked to make sure the rears are working? increase the rear line pressure it sounds like the fronts are not getting help from the rear...also are the rears adjusted correctly? I know sounds simple but you never know! Ive done a few conversion with no troubles im about to put a set of ford cobra brakes on my early mustang 4 wheel disc 13 in front rotors 11.65 rear fronts dual piston 38 mm 15/16 master is whats recomended...im thinking a hydro boost setup will be the way to go. its basically the same system on late model cobra mustangs and that car stops on a dime and gives u back 8 cents!