M20 / M21 / M15 ● Confirmed

Buick · Regular Production Option

4-spd wide / 4-spd close / 3-spd manual (RPO)

Years 1970–72 Models 1

Documented applications

Skylark / GS →

• 1970–1972 ● Confirmed

  GS

This page aggregates every documented appearance of M20 / M21 / M15 in the Buick reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.