While there were no major differences in the ’71 and ’72 Mach 1s externally, the 1973 Mach 1 did receive some significant appearance updates.
New for 1973, Ford offered a “Tu-Tone” hood paint treatment option that consisted of the black or argent paint treatment and twist locks, but without the actual functional components of the Ram Air system. The rest of the car had lower body accent paint and bright trim and the entire car was one color top to bottom. All ’73 Mach 1s received a wide body-side tape stripe in either black or argent, that featured a “MACH 1” cutout on the front of the quarter panel, and a standard “MUSTANG” script emblem on the fender. The deck lid tape stripe was revised, with the “MACH 1” lettering now incorporated into the passenger side of the stripe, instead of centered above it as in 71 & 72. The valance cutouts and bright tips were no longer available on 4V cars for 1973.
1973 Mach 1 engine options remained virtually the same as in 1972, with the exception of the 351HO being dropped. The 351-4V was not advertised in the ’73 Mustang as a Cobra Jet engine even though the 1973 Ford shop manual and other internal Ford documentation did reference the engine as the 351-4V CJ since the “Cobra Jet”. Due to trouble getting the Ram Air option approved for emissions reasons, the 351-2V was the only engine available with Ram Air.