Power booster/ master cylinder ID tag help please

Three brake boosters were used for the 1976 model year. The early version was part number 3580339 which was used until 12-1-75. After 12- 1 -75 Chrysler used two new part numbers. 4026640 for the 6 cylinder cars and 4026641 for the eight cylinder cars. As said before, get your booster rebuilt. The master cylinder for that year was part number 3699228; the casting number was 3699208. It is available from Arizona Parts Nos Mopar. Also look for the casting number on the bottom of the master cylinder to see if it is still the original one.