The prior owner of our 73 Mach 1 installed an oem (off a wrecked car) 71Mach 1 flip-lid cap on ours. It looks and works great. Seems to me I heard to install a 71 flip-lid was a PITA. Perhaps for the non-oem units out there. In any event, I HATE the twist off cap on our 73 Convertible, even...