The Buick Special was named Motor Trend Car of the Year in 1962. Also in 1962, Wildcat was introduced as a trim level on Invicta and became its own model the following year. 1963 also saw the introduction of the Riviera as its own model. In the mid-1960s Buick started officially selling German-built Opel cars through its North American dealerships. For 1967, radial tires became available as an option on all full-size Buicks. The 1970s saw a number of new models added to the Buick lineup including the Estate Wagon as its own model in 1970, Centurion in 1971, Apollo in 1973, and Skyhawk in 1975. 1975 also saw the first appearance of the "Park Avenue" nameplate for Buick as a trim/option package on the Electra 225 Limited. A Buick Century paced the Indianapolis 500 race not once but twice in the mid 1970s. For 1976, Buick began selling rebadged Isuzu Geminis as Opels to replace the Opel Kadett models it had previously marketed. The following year, Electra 225 and LeSabre were redesigned and downsized and the Buick brand saw its best model year sales to date with 773,313 vehicles sold. 1978 marked Buick's 75th anniversary and welcomed a redesigned Century as well as a redesigned Regal coupe which was now available with a turbocharged V6 engine. Buick model year sales broke another record in 1978 with 795,316 vehicles sold. For 1979, the Riviera was redesigned; Riviera S-Type was named Motor Trend Car of the Year. In the 1980s, Buick's lineup saw several changes including the downsizing of various models. In 1980, Lloyd Reuss was appointed as general manager and further pushed Buick into turbocharging, racing, and performance production cars, building momentum which continued a number of years after his departure in 1984 as he headed toward a brief term as GM president. Also in 1980, the Diesel engine becomes available on select Buick models and Somerset is introduced as a trim/option package on the Regal Limited. In 1981, the T-Type performance trim is introduced on the Riviera. Regal was the official pace car of the Indianapolis 500 race in 1981. In 1982, the Grand National high performance package is first offered on Regal. A soft-top Riviera helped lead the return of the convertible, which had disappeared from domestic lineups in 1976. The following year, a Riviera convertible with a twin-turbo V6 paced Indy 500.