If you call a Ford dealer they will tell you 98.2", but a 97.5" belt is what most autoparts stores will sell you and they will work fine. I see here where someone recommenced a Gatorback but I would like to recommend a Gates Poly V-belt. I have had two cars since 1989, both Mustang GT's and both have run Gates serpentine belts exclusively. One car had 130,000 miles on it when I sold it. After changing the factory belt, that was in horrible condition at 30,000 miles, only had to change belts twice more with Gates. The one I took off at 100,000 miles looked in great shape and I sold the car with the second swap on there. My father in-law, also a career car guy who taught an engine repair class at a local community college for 20years, swears by them. You can find them at www.oreillyauto.com or at NAPA.