sold in 1968. Full-sized Pontiacs were also restyled but retained the same basic under-body structure and chassis that debuted with the 1965 model — the roof-lines for the four-door pillared sedans and Safari wagons were the same as the 1965 models, while the two-door semi-fastback design gave way to a squared-off notch-back style and four-door hardtop sedans were also more squared off than 1967 and 1968 models. The GTOs and Firebirds received the Ram Air option, the GTO saw the addition of the "Judge" performance/appearance package, and the Firebird also got the "Trans Am" package. Although originally conceived as a model to compete in the Trans Am racing series, in a cost-saving move the Pontiac Trans Am debuted with the standard engines. This year also saw DeLorean leaving the post of general manager to accept a similar position at GM's Chevrolet division. His replacement was F. James McDonald. Pontiacs built in the late 1960s conformed to new U.S. Federal Motor Vehicle Safety Standards. These included energy-absorbing interior parts such as steering columns, steering wheels, knobs and handles, dual-circuit hydraulic brake systems, shoulder belts, side marker lights, and headrests. The 1969 Firebirds received a heavy facelift but otherwise continued much the same as the original 1967 model. It was the final year for the overhead cam six-cylinder engine in Firebirds and intermediates, and the Firebird convertible (until 1991). Production of the 1969 Firebirds was extended into the first three months of the 1970 model year (all other 1970 Pontiacs debuted September 18, 1969) due to a decision to delay the introduction of an all-new 1970 Firebird (and Chevrolet Camaro) until February 26, 1970. In addition in the late-1960s, GM directed their GM and Pontiac divisions to develop concept mini-cars called commuter cars for urban drivers. GM developed a gasoline-electric drive hybrid, the XP-833, and the Pontiac X-4, a rear-wheel drive mid-engine car that was powered by a radical X-shaped aircraft type air-cooled two-stroke radial engine where the standard crankshaft was replaced by a unit called a Scotch yoke. While the GM car was fully tested, the Pontiac concept was not. Neither was placed in production. 1970–1982 Increasing insurance and fuel costs for owners decreased demand for muscle cars, along with Federal emissions and safety regulations, put an end to the unrestricted, powerful engines of the 1960s. Safety, luxury, and economy would become the new watchwords of this decade. Engine performance began