73-76 A-body discs definitely add to the track width. I think I've seen claims from 1/2" to 7/8" per side.I have 215-60X15 on factory steel wheels, 15" x 7", 4-1/4" BS, on a 68 cuda w/ 73-76 discs. LF definitely hits the front lip when backing out of a drive with the wheels turned. RF just barely clears by about 1/8". No problems when just driving forward, only in reverse. Must be a little flex somewhere allowing the wheel to move though the front end is pretty new Moog including the rubber strut rod bushings.