[The Champ]

I agree with b-man, that a 15x7 is the better option with the tire sizes you are considering.

Summit has the Wheel Vintique Rally I wheels in 15x7 with 4.25" BS or the 15x8 with 5" BS.

I have run 235/60's on the front wheels and 255/60's on the rear on my '64 GTO with the 15x7's with 4.25" BS without issue. Currently running 215/55/17's on the front and 245/50/17's on the rear with 17x7's with 4.625" BS. I do have the wider 12 bolt rear, so if you have the correct rear for your '67 GTO you have more room than I do.

First two photos are with the 15's. Last photo is with the 17's.