72 rear end

[72blue]

Is it just me or is my rear in my 72 half ton 4x4 3" narrower than the front? I am trying to get some wheel ideas and my buddy's 10" mags on 35 bfgs barely stick out in rear (fleet side) and stick out approx. 2.5" up front. I did put a 14 bolt sf in rear, so the rear isn't stock, but it measures exactly the same as the 12 bolt that was in it, measures 64" from flange to flange. Just wondering if maybe that the isn't correct rear track width.

Thanks,
James