Upper Control Arms

Adam, I am almost 100% sure (never say never with mopar) that 73 and up A-bodies went to the bigger Ball Joint regardless of whether you had disks or not.

Moog P/N K772 is listed for;
62-79 B body
65-73 C body
70-74 E body
73-76 A body (no mention of brake type)

Moog P/N K704 is listed for;
68-72 A body only

Even with 9" drums the only change would be to drill out the hole in the spindle to accept the larger joint, doesn't seem to make sense to inventory two control arms and two ball joints to avoid a minor modification to a machining operation.

Red, Control arms are not specific to the type of brake.

Prior to 73 there were 9" drums, 10" drums and disks. The same spindle was used for the 10" drum and disks, 9" drums had there own spindle. The all used the same control arms.

Starting in 73 there were only 9" drums and disks and each type had there own spindle the lower control arm remained the sam as before but the upper control arm was changed to accomodate the bigger ball joint.

The disks were of a different design than the 72 and earlier disks. The 73 and up disk brake swap with the 73 up upper control arm is a popular swap onto 72 and older cars because the rotors and calipers are more readily available and are quite a bit cheaper plus the 73 up design is more trouble free.

If you are looking to swap disks onto your 76 it should just be the matter of locating the disk brake spindles and caliper brackets. Calipers, rotors and breaks can be purchased at Autozone (or what ever chain you frequent).