The Gran Sport, previously an option package available on the Skylark, became a separate series. In a reshuffling of models in the lineup, the Special Deluxe replaced the previous Special. The Skylark nameplate was shuffled down a notch to replace the previous Special Deluxe. The previous Skylark was replaced by a new Skylark Custom.
The basic Skylark was available as a two-door hardtop coupe or a four-door sedan. The Skylark Custom came as a two-door convertible coupe, two-door hardtop coupe, four-door hardtop sedan, or four-door sedan.
The previous V6 was discontinued and the associated tooling was sold to Kaiser Industries, which used the V6 in its Jeep trucks and sport utility vehicles. The base engine in Buick Skylarks (and Buick Special sedans) became a 250-cubic-inch inline six-cylinder engine using a 1-barrel Rochester carburetor (borrowed from Buick’s sister Chevrolet division) that produced 155 hp (116 kW) at 4200 rpm.
Optional on the Skylark and standard on the Skylark Custom was a new 350 cubic inch V8 engine using a 2-barrel Rochester carburetor that produced 230 hp (170 kW) at 4400 rpm. This engine was based on the previous 300- and 340-cubic inch-displacement V8 engines. The Buick Special name was dropped after the 1969 model year.
Source: Wikipedia, 2012