I am working on a 1970 corvette and I want to change the manual brakes to power brakes. I am purchasing the brake booster. I would like to know if there is any special numbers on this booster for this year or is it the same booster they used from 1968 to 1976? Also, power valve. Should it be white or painted black with a square in the middle or an "X". Which one is right? Thank you for any help.