and 1972. The valance cutouts and bright tips were no longer available on 4V cars for 1973. The Mustang needed to comply with new NHTSA standards, which necessitated a redesigned front and rear bumper. The front bumper on all models was now a much larger body-colored urethane unit, mounted on impact-absorbing struts. Due to the revised bumper, the Mach 1 sport lamps were deleted and all models had the park/turn signal lamps moved from the front valance up to a vertical orientation at each end of the grille. The Mach 1 grille was black with a honeycomb pattern and a small running horse tri-bar emblem. The rear bumper was mounted on extended brackets which caused the bumper to protrude from the body further and yielded a large gap. To rectify this, Ford used a body-colored urethane filler piece at each quarter panel, and a sheetmetal filler panel bolted to the taillight panel. 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" nomenclature did continue on in Torino, Cougar, and Montego lines. Due to trouble getting the Ram Air option approved for emissions reasons, the 351-2V was the only engine available with Ram Air. 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. Engines The chart does not reflect the Boss 351 variant of the 351 Cleveland or 250cid I6, as neither were available in the Mach 1 package. The 1972 R-code 351HO package – essentially the solid-lifter Boss 351 engine from 1971 with a reduction in compression from 11.0:1 to 8.8:1 – is listed here, as it was available with the Mach 1 package that year. Second generation (1974–1978) The Mach 1 name continued with the advent of the Mustang II in 1974. The downsized vehicle – fitted with the 2.8 L V6 rated at – outsold the Mach 1 models of the previous four years. For model years 1975 through 1978, the high-performance package was renamed "Cobra II". The 302 Windsor returned in 1975, rated at and of