8.75 diff - metal in oil (pictures). Is it ruined?

Is that a line-up tube inside the main tube? As in a support work for the width adjustment?
As to the clocking of the bearing houses that's not a big deal.
As to the centering of the banjo between the perches, that can be a big deal, but if the current placement centers the flanges in the wheelhouses such that the tire to wheel lips are centered then no biggie
As to the perches being welded on correctly, the spring mounting surfaces should be on the same plane, in side view. I'm trying to think if a degree or two would be a problem but can't come up with anything. Too much, I can see pre-loading one of the springs, which might not be a good thing, with performance springs, especially if it is the wrong side,lol.