Diferential off center??

[Hi-po SS 454]

On measuring for new wheels on rear, I find that correct back spacing measurement for each side on my 71 Chevelleis diferent by 3/4 inch. The passenger rear wheel is closer to outer wheel well lip than drivers side. Fitting a 10 inch wheel which is actually a total of 11 inch from tip to tip, the driver side is happy with 5.75 BS where the pass side is happy with 6.25. Was going to go with a happy medium of 6 inch back spacing on rear wheels.
Is this problem out of the ordinary??
Is there a problem in the suspension somewhere or no big deal???
Also I think I found my leaning problem. High on right rear and lower on left rear by and inch.
I can see the right rear spring has tight coils than and a 3 inch gap to next coil where the driver side has tight coils than a 2 inch gap to next coil, that can't be good.
Can I hear some thoughts on these problems please.



I want to replace rear springs BUT I don't want the ass end up in the clouds if I buy stock rear springs. Was thinking of going with 2" lower springs hoping they settle with wheel well lip just below the top of tire. Hope there some A-body guys out there.
ANY help will be appreciated.