UPDATE:

I received a new-used rear end and they put it all back together with new gears and such. I've driven it several times after I got the car tuned right and the trans shifting so-so. The rear end feels fine & seems to hook up good, but I have a question: The rear seems to be off a little to the rear of the car and further back on the passenger side. It looks like it's tracking to the right - off center (not being parallel to the rear bumper). I measured the gap between the tires and the wheel openings and the right side is further back than the left. Both sides are off-center to the back at least 1/4". It's noticeable (my friend noticed it first). It's like the '94-'96 Impala SS rear end problem, but even worse 'cause it's back further on one side. DOH!!

Can this be fixed?? The only thing I can think of is the subframe connectors are mounted too far back? They had to remove the passenger side SFC and modify the front to clear the y-pipe. We only noticed the rear being off after they installed the new-used rear and modifed the SFC. I also had them install relocation brackets for the LCAs at the same time. Could this also be part of the problem?