Story
The 1973 GTO was a factory performance option on two new Colonnade bodies: the LeMans Coupe and LeMans Sport Coupe. Pontiac included a 230-net-horsepower 400 four-barrel, a heavy-duty floor-shifted three-speed, dual exhaust, power front-disc brakes, 15x7 wheels, G60-15 tires, firm-control shocks, large stabilizer bars, a blacked-out grille, NACA-style hood ducts, and GTO identification. The Sport Coupe added fixed louvered rear quarter windows and offered notchback-bench or Strato-bucket interiors; the plainer Coupe used exposed fixed quarter glass and a bench-seat cabin.
The optional 455 made 250 net horsepower and 370 lb-ft but required Turbo Hydra-Matic. The standard 400 could use the three-speed manual, optional four-speed, or automatic. Pontiac advertised an SD-455 and functional Ram Air during development, but neither reached regular GTO production. A restored car with SD hardware is therefore a recreation or prototype tribute unless extraordinary factory evidence proves otherwise.
Only 4,806 GTOs were built: 494 Coupes and 4,312 Sport Coupes. Hemmings reports 4,262 with the 400 and 544 with the 455. The VIN identifies body and engine, not the GTO option itself, so authentication begins with PHS or original order records and then reconciles the body tag, engine and transmission stamps, axle code, dates, paint, trim, hood, badges, and chassis equipment.