We went with a 17x7 front wheel w/ 4.25" bs on a 225/45/17, and an 18x8 rear w/ 4.75 bs on a 245/45/18.
We also installed an 8.8 rear out of a 94 Cobra that measures 1" wider.
Our rear wheels actually have a different offset than what you need.
On any 8" wide wheel for a 65-70 stang should yield a 4.5" bs.
See the charts below (I hope the links work).
They are extremely helpfull.
http://links.vintage-mustang.com/images/wheelsizes.jpg
http://www.allfordmustangs.com/forum...guide-65-6.pdf