I am not sure if Mark is taking new work yet, but Georg Esterer
orangefj45, is as good as they come and is in your area, I believe.
I believe the caster kit this guy is talking about is a shackle inversion kit... this is not necessary. You need (preferably steel) spring shims that go between the perch and the leaf springs. That is a few buck for the perches and maybe a couple hours work to install them, tops. I
I really want to see pictures of this spring perch. If they were welded on a 1/4" one way or the other, maybe but how bad could it be skewed to cause that much of an issue is tough to understand.
You might be ahead of the game finding a whole rear axle housing and stuffing your stuff into it... I got a rear housing last year for a six pack. You might even go with a loaded one for a couple to a few hundred and have a spare diff and axles on the side as a result.