I put 17x9 with 5.25 backspacing on back and 17x8 with 4.5 on the front of my 70 Cuda, no issues whatsoever. To me, the key to running 17's and looking good is to use a tire with some sidewall height. 45 aspect tires are too short, I would not use less than a 55. I bought a 69 Sat that had 17's on it with properly sized tires and most folks never notice it. There is a huge difference in the amount of tires available in 17 compared to 15". With a v or z rated tire, the difference in handling is very noticable also.