declining in 1971 when GM mandated that all engines be capable of using lower-octane unleaded gasoline, which led to drops in compression ratios, along with performance and fuel economy. This, coupled with trying to build cars as plush as GM's more luxurious Buicks and Oldsmobiles, contributed to the start of a slow decline of Pontiac in 1971. In mid-1971 Pontiac introduced the compact, budget-priced Ventura II (based on the third generation Chevrolet Nova). This same year, Pontiac completely restyled its full-sized cars, moved the Bonneville, and replaced it with a higher luxury model named the Grand Ville, while Safari wagons featured a new tailgate that lowered into the body while the rear window raised into the roof. The 1971 through 1976 model full-size station wagons featured a 'Clamshell' design where the rear power-operated glass slid up into the roof as the tailgate (manually or with power assist), dropped below the load floor. The power tailgate, the first in station wagon history, ultimately supplanted the manual tailgate, which required marked effort to lift from storage. The 1972 models saw the first wave of emissions reduction and safety equipment and updates. GTO was a now sub-series of the LeMans series. The Tempest was discontinued, after being renamed 'T-37' and 'GT-37' for 1971. The base 1972 mid-sized Pontiac was now called LeMans. James MacDonald left the post of general manager to be replaced by Martin J. Caserio in late 1972. Caserio was the first manager in over a decade to be more focused on marketing and sales than on performance. For 1973, Pontiac restyled its personal-luxury Grand Prix, mid-sized LeMans, and compact Ventura models and introduced the all-new Grand Am as part of the LeMans line. All other models including the big cars and Firebirds received only minor updates. Again, power dropped across all engines as more emissions requirements came into effect. The 1973 Firebird Trans Am's factory-applied hood decal, a John Schinella stylized interpretation of Native American bird designs, took up most of the available space on the hood. Also in 1973, the new Super Duty 455 engine ("Super Duty" harkening back to Pontiac's Racing Engines) was introduced. Although it was originally to be available in GTOs and Firebirds, only a few SD 455 engines made it into Firebird Trans Ams that year. One so equipped was tested by Car and Driver magazine, which proclaimed it the last of the fast cars.