Rear axle is 7/16” off center

[Lowellguy1]

Hello, I have a 87 R10  (rear axle flip) with a 12 bolt (5 lug) that I cannot verify it’s part number because it isn’t  located where it should be.  This leads me to believe it could have been a swap from another gm vehicle. All mounts are oe and the locations are centered (based on the C/L)  of the pinion.  When I compare the inside distance from the tire to the frame rail they differ by almost 7/16” It might seem minor but I have the widest wheel possible to tuck in there with the stock wheel well and it is almost hitting the bolts on the inside (drivers side).  Yes the bed is squared and centered on the frame rails.   

Any suggestions are always appreciated.
Thanks


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[Captkaos]

12 bolt truck axles were ONLY used in trucks and only in leaf spring configuration from 1973-81 (previous years GMC's had them also).
If the spring perches are factory and they are spaced correctly on the axle, then I would start suspecting frame damage, worn spring bushing, bent shackles, or the flip kit is not centered.
NONE of these are going to be "perfect", but I would advise that you have room for tire deflections when trying to stuff the biggest tire possible for what you are finding.

Are the flip kit perches welded in and meet up to the saddles properly?