Hello, after much research and help from other Buick folks, I upgraded to 17" wheels on my 68. They fit great and just wanted to share info for anyone else considering it. I went with the VN501 wheels from American Racing. 17x9 rear with 5.47" backspace and 17x8 front with 4.5" bs. Tires are 275/40 and 245/45 and these sizes have exact same diameter, just not as wide up front. Others have used 17x9 up front but didnt want to push my luck. Plenty of clearance on rears inside and out. Might get by with 5" bs on rear but would be pretty close to quarter lip. Tire is centered up pretty good as is. Thanks Jeff