Mercury Built Only 2,250 Cougar Eliminators in 1969 — This One Traded Its Rare Factory Boss 302 for a Swapped 351 and Nobody Knows Why

A Bright Yellow 1969 Cougar Eliminator is headed to a no-reserve auction with its original G-code paperwork intact, proof it left Dearborn with Ford’s rare Boss 302 and a mandatory four-speed. Somewhere along the way that engine vanished in favor of a 351 and an automatic, and nobody wrote down why. Whoever buys it next has to decide whether the car’s real value is in what it is now, or what it once was.

Mercury built only 2,250 Cougar Eliminators for the 1969 model year, and the rarest of them left the factory with an engine most people don’t even associate with Mercury: the solid-lifter Boss 302 borrowed straight off the Mustang assembly line. This Bright Yellow example was one of those cars — a genuine G-code Eliminator, ordered with the mandatory close-ratio four-speed and 3.50 Positraction rear end that Ford required alongside it. Somewhere in the decades since, that high-winding 302 disappeared. In its place sits a 351 cubic-inch V8 backed by an automatic transmission, a swap that turned a factory race-bred coupe into an easy Sunday cruiser. Now the car is headed to a no-reserve auction with its original broadcast sheet still attached, and the question facing whoever buys it isn’t whether the Eliminator badge is real. It’s whether to put the 302 back.

A Factory Race Engine Under a No-Reserve Sign

The walkaround, filmed by dealer High Octane Classics ahead of a Barrett-Jackson Las Vegas sale, treats the Cougar less like a sales pitch and more like a case study. The presenter works around the car panel by panel, pointing out the Eliminator’s factory stripe package, styled steel wheels, and the front air dam and rear spoiler that came bundled with the option, before getting to the part that matters most: what’s actually under the hood versus what left the factory in it.

That distinction is the whole story here. The car’s data plate and broadcast sheet confirm the G-code designation, Mercury’s internal shorthand for the Boss 302 option, along with the four-speed and Positraction axle Ford required buyers to take with it. But the engine bay today holds a 351 V8 paired to an automatic — a combination nobody could have ordered from the factory in a Boss 302 car. Whoever performed the swap left no paperwork explaining why, which is exactly the kind of gap that turns a simple muscle car sale into a genuine research project.

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Mercury Built Five Engines for the Eliminator — Only One Came With an 8,000-RPM Tach

Mercury’s Eliminator started life as a Los Angeles Auto Show concept in October 1968, all blacked-out grille and body-color stripes over a Cougar that had spent its first two model years playing the restrained, upscale alternative to the Mustang. The production version arrived midyear in 1969, and Mercury sold just 2,250 of them before the model year closed, a fraction of Cougar’s total output and proof the Eliminator was built to grab attention more than to move volume.

What made the Eliminator different wasn’t one engine, it was the choice of five. Buyers could start with a 302 small-block, move up to the standard 351 Windsor four-barrel, step into a 320-horsepower, 427-lb-ft 390 big-block, or go straight to the 335-horsepower 428 Cobra Jet — Mercury’s genuine muscle car answer, capable of high-13-second quarter miles when ordered with the Super Cobra Jet’s ram-air induction. Then there was the fifth option, added late in the model year almost as an afterthought: the Boss 302, borrowed from the Mustang parts bin and rated at 290 horsepower with a redline near 6,250 rpm and an 8,000-rpm tachometer to match its high-winding, solid-lifter nature. Ford required the close-ratio four-speed and 3.50 Positraction rear whenever a buyer checked that box — exactly what this car’s original paperwork shows it left the factory with.

The Eliminator Equipment Package itself was pure late-1960s muscle car theater: a front air dam, body-color rear spoiler, styled steel wheels, a blacked-out grille, a hood scoop that only functioned with the ram-air 428 Cobra Jet, a racing-style remote mirror, and Eliminator-specific stripes in white or black laid over whatever color the buyer chose. Bright Yellow, like the car in this video, was one of four factory colors offered, alongside Competition Orange, Bright Blue Metallic, and white.

None of those five engine options existed in a vacuum. Ford built the Boss 302 to satisfy SCCA Trans-Am homologation rules, which required a manufacturer to sell a minimum number of street versions of any engine it wanted to race. Mercury’s Trans-Am effort never carried the same weight as Ford’s factory Mustang program, but putting the same engine in the Cougar Eliminator meant Mercury dealers could sell buyers a genuine piece of that racing technology without ever setting foot near a race track. It is part of why the option arrived so late in the model year and in such small numbers: it was added almost as an afterthought once the parts were already being built for Dearborn’s Mustang line.

Numbers-matching muscle cars from this era carry a real premium at auction precisely because so few survive with their original drivetrains intact. Decades of engine swaps, wrecked blocks, and owners chasing more power meant plenty of genuine Eliminators eventually lost their factory engines the same way this one did, whether through a blown motor, a cheaper rebuild, or simply a previous owner who wanted an automatic for daily driving. A car that still carries its original broadcast sheet and data plate, even with a different engine currently installed, gives the next owner a documented path back to factory specification that a car with no paperwork simply can’t offer.

Why a 351 Automatic Is the Wrong Answer for a Boss 302 Car

The Boss 302 is the reason this particular car matters more than its current drivetrain suggests. Ford built the engine by mating the 302 Windsor block to cylinder heads borrowed from the 351 Cleveland, with bigger valves and better ports than a small-block V8 had any business carrying in 1969, then tuned the combination to rev harder and breathe better than almost anything else Mercury sold that year. It was never about torque or stoplight bragging rights. It was built to turn Trans-Am racing credibility into showroom Cougar sales.

That’s what makes the swap in this car such an odd trade. A 351 automatic is a perfectly good muscle car engine and transmission combination, comfortable and torquey and easy to live with, but it’s the opposite of what a Boss 302 buyer signed up for in 1969. Whoever owns this Eliminator next inherits both halves of that story: the paperwork proving what Mercury built, and the drivetrain proving what happened to it since. A full return to G-code spec would mean sourcing a period-correct Boss 302 and matching four-speed, a project measured in years and real money. Left as-is, it’s still a numbers-matching-body Eliminator with documented factory history, which counts for plenty at a no-reserve auction even with the wrong engine between the shock towers.

Watch the full video above and let us know your thoughts in the comments.