For 1978, Chevrolet added a new front and rear bumper and added a hood scoop unlike the 1977 with only a decal. Sales topped all previous models with 272,631, 54,907 of those are the RPO Z28 "Special Performance Package".
Available models for 1978 included Sport Coupe, RS, Type LT, Type LT/RS and Z28. Although some believe you could order a "Type LT/RS Z28", that is false. The Z28 had a stripe package that you could not delete, so the two tone paint of the Rally Sport (RS) would interfere. The Z28 had a 350ci that produced 185 bhp and produced 280 ft.lb. of torque, which ran with a four-barrel Quadrajet carburetor. Z28s transmissions were either 4-speed, or a TH-350 3-speed.
Source: Wikipedia, 2011