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

Just so you know;
I have done this swap twice; once on an E-body, swapping the calipers to the back, and
once swapping F-body brakes onto an A-Body
Both went without a hitch.
Point being that the Factory parts do fit. So, hang in there, The guys will try to figure it out with you.