New dual round taillights were integral with the back bumper. Because SS models suffered heavy insurance surcharges, Chevrolet introduced the “Heavy Chevy” at midyear, which was based on the base Chevelle, and was available with any V8 engine except the 454, which was exclusive to SS models. The Heavy Chevy (RPO YF3) was ONLY available with the base Chevelle sport coupe (13437) and was primarily a dress up option and even it was limited to options available on the standard Chevelle sport coupe; no carpeting, no bucket seats, etc. For 1971, the SS option was reduced to one RPO code, RPO Z15, and was only available for the Chevelle Malibu. This RPO code required any optional engine and transmission available in the Chevelle lineup. Since the 307 V8 was the standard base V8 in 1971, it could not be ordered with the SS option; one had to order one of the two 350 V8 engines (L65 or L48), the LS3 402 or the LS5 454.
