8.75 Not centered?!?!

Hello. I recently purchased a Moser fabricated 8.75 and am in the process of installing it in my '73 Dart. I had it made to optimize the wheeler space with a 15x8.3 Weld S71 and 255 60 ET Drag Radials. I got everything mocked up - spring perches @ 42" and u-bolts snugged up, offset shackles, I haven't gotten My Dr. Diff offset front hangers yet (trying to determine everything will fit) but I have the original front hangers in place and against the frame. The wheels are bolted to the axles and slid into the housing (no carrier yet) and against the snap ring. My problem is the passenger side is about 1/2 - 3/4" closer to the outside fender. Was planning on Dr. Diff rear Cobra disc brakes but now it will hit. The spring perches must be set equal distance from the housing ends correct? Is there any other way to center the rear? Can't really move it to the driver side because it's already very close to the springs. Stuck and not sure what to do. I'm planning on SS springs with poly bushings but am just using the stockers for mocking. As always, any advice, experience, knowledge, and prayers is greatly appreciated! Been a while since I've messed with this stuff but I don't remember it being this tough?

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