Thanks again for the advice. I am going to order custom redlines, so unfortunately, I'm not going to be able to do any trial fitting first.

Right now I'm leaning towards the 225/50/17 and 255/45/18 in the GY F1 GS-D3. I will search for a taller rear tire, but I haven't found any matches yet in a performance tire, at least not with GY or BFG.

Not trying to push you one way or the other but an option to get you to taller tires would be:
225/55/17 front
255/55/18 rear
Nice rake, period look in sidewall height, would really fill the wheel wells.

Not sure how much more room is in a 67 wheelwell but this client of ours fit a carefully measured 295 on the back of his Pontiac A-body
https://lateral-g.net/forums/showthread.php4?t=14437