Here is a quote from a Q&A forum in my recent issue of Hemmings Mustang Marjet and Tech guide. hope it helps....Lee
I've got a 1968 Mustang coupe. It's an original V-8 car with five-lug hubs and suspension that I have upgraded with a 5.0 liter engine, I'd like to put some rims and tires on it, either something like the late Cobra R rims or Torque Thrust II's. What is the biggest rim size that will fit front and rear and what is the biggest tire I can get on them without hitting the fenderwells?
It is our experience that you should be able to use 16x7 inch wheels front and rear if you use 225/55R16 low profile series tires.
Have 16X8 with 4.5BS on 68 Mustang. Using
225x55x16 tires. It's a tight fit on the
front, but the car is low. The back is not
a problem. Car also has Global West upper
arms which are slightly shorter than stock.
I did run the 16X8's on there before going
to the GW upper arms, but the car wasn't
quite so low. It was an ok fit but you'd
get occasional tire rub. With 16X7's you
might be ok all the time- unless the car
was really low. (top of the ft tire inside