I autocross a 72 240Z, it has been lowered 1-1/2. I am currently running 225/50-16,.. 7 x16 wheels. I was told to go to 255 series 16.I can get a set of those to see if they'd clear the wheelwells. I do not want to cut up the car. I was told by a 3 time National Champion, who used to run a 240 that i should go to 8-1/2 x13 rims.He said he had seen Z's running 13 rims. We measured his and my tires and found almost a 4 difference. That would mean the center of gravity would be lowered by almost 2. I have a 3.55 diff,and the larger tires lower it, where as the 13 would make it accerate quicker. Question is would 13 fit and what kind of offset would be needed?