I am running Foose Nitrous IIs on my 66 GTO.
https://lateral-g.net/forums/showthread.php4?t=16289
They are 18x8s with 225/35/r18 BFG KDW (front) and 20x10s with 265/30/R20 BFG KDW (rear). They are a custom backspace front and rear. Even at the lowered ride height, they still have not rubbed. the rears have about 3/8" of space on either side of the sidewall and sit up inside the fenderwell. the fronts can turn lock to lock and not hit anything, but only the tire sidewall is inside the fenderwell. we bought one of those Wheel-Rite measuring tools and ordered the wheels based on those measurements. i would highly recommend using this tool.