Low pedal power brakes

I'm not sure how much the brake pedal should travel before braking is started. It definitely moves farther than our newer vehicles but the car stops very well. It just seems like there is way too much power assist. I've thought about restricting the vacuum line to the booster, but I'm not sure that would affect the amount of assist. I think it would just take longer to recover after a stop. I think you're on the right track about the prop valve, like maybe the residual pressure portion for the rear brakes was not holding pressure before the rebuild. Although the rubber seals all still seemed pliable and intact, its possible they could have shrunk.