I have a 71 olds supreme. Looking to buy a set of boss 338's 18x8 fronts and 20x10 rear. Is that a good fit? Don't want the rear wheels to hang outside of the fender wall.

 

You will need at least a 5.5 offset for the 10 in the back. I have 15x8 on the back of mine and I think the offset is 4.5

 

Subscribed, I'm looking at 18's but 20's on the rear might be cool.. I hope you post pics and back space info..

 

I have 15x10's on the back of my '70 with 295 50 15s, they do not "hang out", and do not rub. As long as you do the math, I don't think you would have any issues. I think Richard (Gearheads78) has a fancy tool used for properly calculating the maximum diameter and correct backspacing available for lease with a substantial but refundable deposit.