In 1973-75 and in 1986, there was a Century Gran Sport. For 1973, Buick renamed its intermediate line from Skylark to Century, a nameplate previously used on Buick's full-sized performance cars from 1936 to 1942 and 1954 to 1958. Like all GM intermediates, the 1973 Century received new Colonnade styling, which amounted to pillared hardtop sedans, coupes and station wagons - each of which utilized frameless windows along with fixed rear side windows, and convertibles were discontinued. The GS became the "Gran Sport" and was now an option package on the semi-fastback Century 350 Colonnade coupes. The "Gran Sport" option included decals on the rear fenders and trunk lid reading "gran sport" along with suspension and appearance upgrades.
The standard engine was a 150-horsepower 350 two-barrel V8, which was the standard engine for all Centurys. In addition to the 175-horsepower 350 four-barrel V8 (with single exhaust), the 190-horsepower 350 four-barrel V8 (with dual exhaust) was available only on the Gran Sport. Two 455 cubic-inch V8s were available including the 250-horsepower four-barrel and the Stage 1 four-barrel rated at 270 horsepower (both with dual exhaust) - all net figures and similar to the 1972 models. More than 700 '73 Century GS models were built with the Stage 1 455, the majority with the three-speed Turbo Hydra-matic 400 transmission and a small number with the four-speed manual transmission.
The 1974 Century "gran sport" received the same exterior and interior trim changes as other Century models. The same selection of engines was carried over from 1973 including the 350 four-barrel, 455 four-barrel and the 455 Stage 1 four-barrel (the 455s downrated to 245 and 255 net horsepower respectively) and, like all other '74 Century GS engines, only available with a Turbo Hydra-matic transmission. Radial tires were a new option for 1974 along with reclining Strato bucket seats.
For 1975, the Century GS, or "gran sport" entered its third and final year on the Colonnade body. It was reduced to a mere appearance/handling package as the 455/Stage I options were discontinued and Buick's revived 231 cubic-inch V6 was the standard engine, mated to a standard three-speed manual transmission or optional Turbo Hydra-matic. The only optional engines were two 350 V8s, a two-barrel 155 horsepower version or the four-barrel option rated at 175 horsepower and offered only with the Turbo Hydra-matic. Both engines were also mated to catalytic converters for the first time this year, which mandated the use of unleaded gasoline and precluded the availability of true dual exhaust systems. Radial tires were now standard equipment and the Strato bucket seat option reverted to the non-reclining version.
Both the Century GS and the larger Riviera GS (which also had been continually produced since 1965) were discontinued after the 1975 model year due to sagging sales for high-performance cars following the 1973-74 energy crisis and subsequent trends toward smaller and more fuel-efficient cars. Performance versions of the Century (and its companion Regal line) and Riviera would return in the late 1970s with the advent of Buick's turbocharged 231 V6 introduced in 1978 on the Century/Regal intermediates and the full-sized LeSabre Sport Coupe and then the newly-introduced front drive Riviera in 1979 for the "S-Type" which later became the T-Type, a moniker that would ultimately replace the GS badge for sporty/performance Buicks in the early 1980s.
The Century GS model returned in 1986 for what was now Buick's front-drive intermediate-sized car (Regal continued as a coupe on the 1978-vintage rear-drive G-body until 1987). The GS was only offered as a two-door coupe and was powered by a fuel-injected 3.8 liter (231 cubic-inch) V6 mated to a four-speed overdrive automatic transmission but with far less horsepower than the rear-drive Regal GN's turbocharged/intercooled version rated at 245 horsepower. This Century GS was a one-year-only offering in 1986 sold alongside the Century T-Type coupe and sedan.
Source: Wikipedia, 2013