When I looked last night in the MPC I only looked for 1969 applications on this particular belt because I was tired and lazy. But with a 68 inch belt its most likely an air conditioning belt application since thats pretty long. The quick reference numbers used on belts typically could have serviced numerous applications so that Ford did not have to stock so many belts, so this JC-684 belt could have been correct for a few applications over the years. Ford also had multiple vendors supplying belts during this period such as Gates, Goodyear, and Dayco.