73 up B and R bodies used the caliper with the low mounted hose, this hits the shock on 66 to 72 B bodies when rear mounted. BTDT
Not sure about A or FMJ calipers

If one is going to rear mount the calipers on 66 to 72, I recommend moving the frame end of the hose to a position forward of the spindles. Basically mirror image of the factory design.