Stage 1 Special Package (dealer ordering code): hotter cam, 11.0:1 compression, larger valves/stiffer springs, rejetted Quadrajet, recurved distributor, functional cool-air induction, 3.64 posi axle, recalibrated TH-400 (higher shift points)

Years 1969–70 Models 1

Also described as Stage 1 Performance Option: 455 "Stage 1" 360 hp, low-restriction dual exhaust, performance axle w/ positive traction, specific ornamentation, H.D. radiator

Documented applications

Skylark / GS

1969 Confirmed

GS 400 only; 1,256 coupes + 212 convertibles, all Flint-built; engine code **RS**

Grade note: single-source (code) / confirmed (package)
1970 Confirmed

GS 455 only; $113.75–$115 over GS 455; engine code **SS**

This page aggregates every documented appearance of A1 in the Buick reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.