How a dealer-tuner brought back the COPO idea.
GMMG isn't a factory. It never was. It's Matt Murphy, a handful of dealers, and the last generation of F-body Camaros and Firebirds — bent into something GM never officially built.
The name
GMMG started as George-Murphy Motor Group — a partnership between Matt Murphy and a business partner whose last name was George. The George partnership dissolved early on, but the acronym stuck. Today, GMMG stands only for the cars themselves.
The idea
In the late 1960s, Chevrolet sold performance cars through a program called COPO — Central Office Purchase Order — that let select dealers order factory cars with off-the-books drivetrain combinations. The most famous cars in Chevrolet's performance history came out of this loophole: the ZL-1 Camaros of Fred Gibb and Dick Harrell. The 427 Yenkos. The Baldwin-Motion Phase III cars from Long Island. The Berger Chevrolet cars from Grand Rapids. Nickey Chevrolet in Chicago.
By the time Matt Murphy started GMMG in Marietta, Georgia, the COPO program had been dead for thirty years. But the model — take a production car, partner with a hungry dealer, upgrade it in a series of documented performance phases, badge and number it, and sell it under a shared brand — that model was still perfectly good. It just needed someone to run it.
The 4th-gen F-body was the last purpose-built American V8 muscle car. Somebody had to send it out the right way.
The dealer partners
GMMG never sold cars directly to the public. Every car was retailed through a partner dealer — the same model that made the COPO cars possible in the first place.
- Berger Chevrolet (Grand Rapids, MI) — the primary Camaro partner, and a name with real 1969 heritage. Berger sold the Berger SS line, and later the Dick Harrell Wide-Body Edition.
- Tom Henry Chevrolet (Bakerstown, PA) — a small dealer with a serious performance following. Home of the Tom Henry SS.
- Carl Black Pontiac (Kennesaw, GA) — GMMG's Firebird outlet. Every Blackbird Trans Am, CETA, and Year One car was invoiced through Carl Black.
- Direct GMMG builds — the DEI Intimidator SS (Dale Earnhardt Inc. tribute), the Hot Rod Edition, and the ZL-1 Super Car ran through the GMMG shop itself.
The build process
Cars arrived at the GMMG shop in Marietta as production-line Camaro SS or Trans Am WS6 units. From there, they entered a phased upgrade path.
Phase I was the bolt-on level: a Whisper cold-air intake, ported MAF housing, ASP underdrive pulleys, ported factory exhaust manifolds, a custom chambered exhaust system, and an LS1 Edit tune. That was enough to walk out of any modified LS1 that arrived on the wrong day.
Phase II got serious. Long-tube headers, catted Y-pipe, ported LS6-spec cylinder heads, a custom camshaft, hardened pushrods, a ported throttle body. On a Hot Rod Edition — a mid-tier build — Phase II showed 435 horsepower at the flywheel on the shop dyno.
Phase III and above are where GMMG went past what a normal shop could deliver. The top phases on the ZL-1 Super Car and the Dick Harrell Wide-Body Edition used GM Racing–derived 427ci all-aluminum LS crate motors — the same short-block architecture as the C5R Corvette race engine — with GMMG-specific tuning and driveline hardware.
Why they matter now
Production per model line ranged from ten to about one hundred. The rarest — the CETA Blackbird — is a run of ten. The most famous — the ZL-1 Super Car — is a run of sixty-nine, keyed to the original COPO number. In the collector market, that scarcity is roughly equivalent to a real Yenko or Baldwin-Motion car from the first era.
The critical difference: GMMG cars are close enough in time that Matt Murphy can still authenticate them personally. Every car has a numbered dash plaque, a signed door-jamb tag, and a paper trail through the dealer. Chain of custody is intact. That's a level of provenance the original COPO cars can only dream about.
The registry
This registry is not a GMMG product. It was started, and is still run, by Jim Smith — an owner of eight GMMG cars, an amateur archivist, and one of the earliest evangelists for the marque. Jim runs the registry with Matt Murphy's blessing but no formal affiliation. The public listing shows first name and state only; verified detail records are released to owners after chain-of-custody verification. Any operating surplus goes to Make-A-Wish.
If you own a GMMG car — or you're considering buying one — the registry is where you should start. Reach out at the registry contact form.