B-body front end parts on an A-body??

In 73 Mopar started standardizing a lot of stuff that was different on A bodies than B or E bodies. Big bolt pattern disc brakes on A bodes therefore use the same upper and lower ball joints as B Bodies. They also use the same rotors, calipers and caliper brackets. There may be small differences in caliper hose routing and proportioning valves but most of the replacable wear items are interchangable. They did something similar when in 72 they went to that universal plastic side marker lens, and no more individual pot metal chrome plated side marker bezels. Now, there was some small bolt pattern stuff still kicking around in the parts bins in 73 so SOME of those lower powered A bodies got small bolt pattern brakes and control arms, mostly on slant sixes. But towards late 74 thru 76 everything pretty much got big bolt pattern disc brakes. that's why a lot of B bodies get upgraded disc brakes by using 73 - up A body spindles, because they used the same upper and lower ball joints and rotors, and because their geometry works on a B body.