Those Pro's have a wider section width than the standard width 275/60 radial. I will be very surprised/amazed if they fit with a 4.5 backspace wheel and the stock 8 3/4 housing and non rolled or cut inner quarter lip. Still waiting the results here though. I am looking to buy tires myself for a 67 Plymouth Belv using an 8" wide 4.5 backspace wheel. I have cut the lip out of my quarters.
