I have two brake boosters, one out of a 72 3.0CSA, the other out of a 74 2.5CSA. Both are approximately 10" (25 cm) in diameter. The booster out of the '72 is approxmately 7" (17 cm) thick, while the '74 version is about 4" (10 cm) thick. Why the difference on two carbureted cars? Is the thinner version similar to the tii dimensions?