18" wheels and tires on a 68 GTO what back spacing and tire size

[moparcolt]

I am building a 68 GTO O for a friend and he wants 18" rims on it. What I want to put a 10" or bigger rim on the back and a 8-9" on the front what will fit?
I want a tallish tire in the back to fill the wheel well nice. car is stock ride height.

Thanks in advance.

Chris

[JustinB]

On 68-72's, we have done 18x9 with 275/35/18 and 18x10 with a 305 in the rear. BS has to be spot on. Feel free to call us if you need help or pricing.

[lemans68]

Any recent pics of the 18" wheels on the gto?