Will It fit

[BSB67]

I was under the GTX tonight and looked closer at the tire fit. The tire sits almost perfectly centered in the wheel well. About 3/4” clearance both inside and outside.

 

[BSB67]

With an aluminum rim, beads are about 1/2", so.... an 8" rim. Steel? Probably an 8 1/2 rim.
Your numbers will vary.

My 7” steel rims measure 8” outside width w/ the bead

 

[Virg464]

Well, the 255's fit nicely using the the 8" police wheels, plenty of room on both sides. One thing I did omit, didn't think of it until I dropped the rear axle to get the slicks out, it's a narrowed 9" rear end, so things may a little off from a 8.75". The axle flange seems to line up with the middle of the wheel well, I assume that's normal.

 

[33 IMP]

Yeah, the narrowed nine is something you probably should have mentioned, lol.
Once a rear is narrowed, "normal" does not apply.
(My narrowed nines are under 40" disc face to disc face, and not in the muddle of the tub, lol)