521 ◑ Single-source

Pontiac · Regular Production Option

Front disc brakes

Years 1967–68 Models 1

Documented applications

Firebird / Trans Am →

• 1967 ◑ Single-source
• 1968 ◑ Single-source

This page aggregates every documented appearance of 521 in the Pontiac reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.