73 E body front disc brakes conversion on A body. Where did I mess up?

I have Proforged lower ball joints on my Duster and have the calipers to the rear. No issue with clearance at all.

It looks like when that particular lower ball joint was spot faced they left a little shoulder, probably wasn’t intentional. It doesn’t serve any purpose so you could just grind that lip down until it clears. As long as you don’t touch the machined surface it won’t make a difference to the mounting. I’ve see a number of different castings and amount of machining done on various different lower ball joints depending on the manufacturer and origin, they’re not particularly consistent with that area. Heck even the spindles vary some with extra casting material depending on the year/model.

Adding washers/spacers there will add negative camber.