And on the early (65-72) A LBJ's there is a different part number for drum and disc but the only difference is the drum unit holes are for 1/2" bolts and the disc unit holes are for 9/16" bolts and there is plenty enough material there to drill em larger and the set I did was soft material (iron?) & the drill bit went thru em like butter so if you have a set of drum ones and are converting to (early) discs no need for another purchase.