That's a BBP rear end, and it's wider so be careful as the measurements aren't really relevant for the OP. The other thing is that regardless of which B body width rear axle that is, you probably can't fit 275's with that backspace. My Duster has a 68-70 B-body 8 3/4, and even before the 1/2" spring offset the backspace to center the 10" wheels was almost 6.5". As it sits now I run 295/35/18's on 18x10's with a 7" backspace. But that's with the B rear, a 1/2" spring offset, and disk brakes (which also widen the track). There's a lot of variables to consider.
