Brake booster and master cylinder assembly

4 wheel drum cars have distribution blocks

Front disc rear drum cars after 69 have proportioning valves

4 wheel disc just use the drum brake distribution block

Early 67-69 had the add on hold off block they were not that good that is why they went to a proportioning valve in 1970. An upgrade for a 69 and earlier if original don't matter. 70-73 pictured below. Its all I use unless 4 wheel disc. Later style 74-76 are much larger and used into the mid 80's

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