1971 was the most heavily restyled year for the E-body Barracuda program — quad headlights replacing the dual round set, a new horizontal grille, the famous gill side-marker inserts on the front fenders (4 'gills' on a 'Cuda, optional). The body shell remained Herlitz's 1970 design but the front and rear bumpers, taillamps, and grille were all new.
Engine availability — period framing: the 1971 Plymouth Barracuda Brochure enumerates 'Cuda powertrains as '340, 383, 440, and 426 Hemi.' The V-code 440 Six-Barrel does not appear in the consumer brochure's engine pitch even though Govier registry counts attest 237 V-code hardtops + 17 V-code convertibles for 1971 — likely a ordering option that wasn't promoted in dealer marketing. After 1971 the 440 Six-Barrel and the Hemi were both gone; 1971 'Cudas with either are the muscle-era apex on the Plymouth side. (198 / 225 Slant Six and 318 also still available on lower-spec Barracuda body trims.)
Production: significantly down from 1970 across the board, reflecting the broader collapse of the muscle market under insurance / emissions / safety pressure. Hemi 'Cuda hardtop 1971 = 108 cars; Hemi 'Cuda convertible = 7 cars. Govier's tables remain the registry-attested baseline.