Bizzarro lowering problem on my Chevy

What Kustm52 says makes sense, 49-52's are that way with that inner bulge.
I had virtually the same thing happen on my 48 Chev, the rear is centered in the frame , I think the body is not centered on the frame, but mine's never been apart, probly came that way from the factory.
The 48 has bigger fender openings tho, so I don't have the mounting problem
, just have slightly more room between the tire and fender on one side. Oh well, you can't see both sides at once, and I'm probly just too damn picky.
If you use a small floor jack out on the road, jack the rearend up under the pumpkin, then place a 4x4 (or 2) under the other rear tire, lower the jack a little until the tight side starts to drop downward, .this will give more clearance on the tight side. This would work out on the road if need be.

 

Chris.
I ran into this very same problem with my 49 ford coupe after I installed a maverick axle. Measured and measured again....left side was about 3/8ths inch closer to the fender lip than the right side or vice versa...I thought the car may have been crashed earlier in it's life but it showed no signs. I agree with Jay....factory sloppy mis-alignment issues.

 

Yo, Chris..
I was able to run 285/70R15s' on my 50 delivery but it took a little BFH work on the inner fenderwells and a healthy slice outta the wheelwell lip on both sides. Left about 1/8th inch lip. The tires rubbed a little inside on sharp turns at speed witha full tank of gas but I really wanted those fattys on there. The only part that touched was the inside shoulder of the tire on smooth inner panels. I really think a 265 or 255/70 would have worked ok.
But then, my car didn't sit low at all.
I used an old 83 cutlass rearend...centered it in the wheelwells when I installed so it as exactly in the center of the body[for body clearance reasons] ...God knows where it was in relation to the chassis..

 

Same thing here on a 49 Ford. One side I can get one finger between the tire and quarter panel, other side two fingers.
The car hasnt been wrecked and it tracks nice. IM thinking its in the springs.
I had it up off the ground and checking it and maybe the springs put a twist on the rear end when its down. I dont know.
I took the rear end loose fromt he springs and did some more checks. It sets on the pins no matter how you jack the springs they are in the same place so maybe if they have an inch of twist it will place it off on one side.
My car sets level, the rims arent bent.