I am having brake issue on my 1970 duster

Did you have no brakes before the install? Definitely not enough info.
we had brakes but they got to where you really had to stand on them to stop
we replaced both the master cylinder and the vacuum booster that came together in a set is it possible that the linkage from inside off the peddle doest match the brake peddle doesn't want to return so the brake lights stay on when you let off the brake peddle