What tires? 74 BB Coupe

245/60 is a better choice, especially since the '74 is like all the rubber bumper cars, higher on the frame. The 235 is a bit small in the wheelwell. The 255/60-15 is run by many as it is much more common and easier to find, but depending on the car, can rub various spots like the front inner fenders and the emergency brake cable bracket on the trailing arm. In '78 when the 255 became an optional tire, Chevrolet trimmed the front half of the upper portion of the front fender lip.

If you run the 255, you need to mount one and trial fit it, checking everything at all four corners. The 245 and the 235 can both rub the frame on full lock turns, but almost all tires will. It is one reason they used carriage bolts to mount the idler arm and steering box.