Yeah, you should be fine with that wheel. I think you could go to a 4" back spac comfortably if you wanted to run a 10" wheel down the road. I had a B Body 8-3/4 in the car before the Dana. I ran a 10" wheel with a 5-1/2" back spacing.
I also ran a set of 8.5 x 26's on a 8" rim, 4 or 4.5" back space....
I also ran a 275/60 MT on an 8" wheel...
295/65 on a 10" rim...
10.5 x 29.5" on a 10" wheel...
Basically, if it fits in the stock wheel wheel well, I have probably tried it. I can't fit as big of tire as I used to now that the car sits a fair bit lower now.
-Kenny