Is the truck a 4x4 or 4x2? There is confusion on the 4x4 trucks in that people ask if it is HEAVY DUTY....only one type of brakes on them, so they were standard, not HD. But some home the terminology carries over....HD had the 2 1/2" as did the 4x4 (standard)......going by memory but the brake parts interchange on these old Ford trucks is a nightmare....lot of bad info, or no info.