What is a GMC Sierra Classic?
Quick Answer
Sierra Classic was GMC's top trim level on the classic C/K pickups, the GMC equivalent of Chevrolet's Silverado package. It added the nicer interior, woodgrain, and brightwork. Sierra began as a trim in 1972 and became the name for all GMC pickups when the GMT400 arrived in 1988.
Sierra was GMC's answer to Silverado.
The trim
On the square-body and earlier C/K trucks, Sierra Classic and Sierra Grande were the upper trims, matching Chevrolet's Cheyenne and Silverado ladder.
The model
From 1988 (GMT400), GMC made Sierra the name for all its pickups while Chevrolet kept C/K. Mechanically the trucks are twins of the Chevrolet.