Re: Finally decided to go with 17 inch wheels
225/45-17 and 255/40-17 is almost exactly stock diameter. If you're lowered at all don't go too much higher in your sidewall or you might rub.
...and that seup, at least in mine, gives you very neutral handling. Extremely controllable and responsive. Surprisingly so for a 45 year old car.
1968 Base hardtop 250 with a P̶G̶ built 2004r
Holley 390 CFM carb
Langdon split header to a 2.5" exhaust