With the Sportsman S/Ts, I can also source 225/70/15s and 235/60/15s.

The rims I'll be buying (again, very limited in selection) are 15x7 with 4" BS and 15x8 with 4.5" BS. I know people have fit 275/60/15s under the 67 B-bodys (although, sometimes with difficulty, hence my choice to stick with 255s), so I'm simply assuming that a 255/60 on a 15x8 with 4.5" BS will fit??? I've been wrong before....

This is why I'm asking these questions, so I can be pointed in the right direction. It's an investment that I can really only afford to make once, so I need to get it right.

Cheers!