Donald Farr
Former Editor, Mustang Monthly
January 1, 2009

I think we can safely say that Eric Petosa is fanatical about originality, right down to stampings, date codes, and even the numbers on brake adjuster plugs. During the restoration of his Boss 302-powered '70 Cougar Eliminator, Eric conversed with experts and even traveled halfway across the country to visit Bob Perkins to track down parts and "Paint OK" stamps to correctly detail his Cougar to fresh-off-the-assembly-line new. Parts were bought and swapped via eBay while a Tupperware storage container became full of notes and documentation. The result is a gem that has been called the "Ultimate Eliminator" by the Cougar Club of America.

Eric didn't need to research and search for parts for his '72 H.O. Mach 1-he bought the 18,000-mile original with 99.9 percent of its original parts still intact.

The air filter is an N.O.S. unit from 1972, as Eric shows while pulling the air cleaner.

The '72 R-code Mustang is one of the rarest yet least understood vintage Mustangs. Ford canceled the Boss 351 after 1971, but began offering a slightly detuned version of the Boss engine, calling it the 351 H.O., shortly after the '72 Mustang introduction. Not to be confused with the hydraulic-lifter 351 4V or Cobra Jet engines, the 351 H.O. closely resembled the previous year's Boss 351 with a four-bolt main-bearing block, solid-lifter cam, aluminum intake, and 4300 four-barrel carb. However, the H.O. was detuned for 91-octane fuel with slightly milder cam specifications along with open chamber heads and flat-top pistons, as opposed to the Boss 351's closed chambers and pop-up pistons, to drop the compression ratio from the '71's 11.1:1 to a more tolerable 8.8:1.

Eric was thrilled to find the original air cleaner decal intact, noting that reproductions aren't available. "They made less than 400 cars, so I don't think anyone fooled with reproducing them," Eric says.

Also like the Boss 351, the H.O. was packaged with extra performance goodies, such as four-speed transmission only, 9-inch rear with 3.91 gears, Competition Suspension with staggered rear shocks, and 15-inch wheels and tires. Oddly, the H.O. isn't identified anywhere on the car's exterior. In fact, the only place to find identification is on the air cleaner decal.

But unlike the Boss 351, which was available only in the Boss 351 SportsRoof package, the 351 H.O. was offered in any '72 Mustang body style, although the majority were ordered for Mach 1s and SportsRoofs. According to Kevin Marti's Mustang...By the Numbers book, production included 13 convertibles, 19 hardtops, and 366 SportsRoofs for a total of 398 Mustangs with the H.O. drivetrain. Of the 366 fastbacks, 336 were Mach 1s.

Strangely, ram air was not part of the package. Instead, the 351 H.O. picked up fresh air from a plastic duct under the battery, which funneled fresh air through a flexible hose into the air cleaner snorkel.

The 351 H.O. engine used a Motorcraft 4300 four-barrel carburetor, rated at 750 cfm, similar to the Boss 351's Autolite 4300.

It's interesting that the 351 H.O. engine is not mentioned in the '72 Mustang showroom brochure. However, by the time Ford released its October revisions for the dealer's Car Facts Organizer, the 351 H.O. had been added to the "'72 High-Performance Engines" section. Output was listed at 275 hp, compared to 330 hp for the previous year's Boss 351. Note that much of the decrease was attributable to the new SAE net horsepower rating, used for the first time in 1972. The Car Facts sheet also provided one reason that Ford dropped the Boss 351: "Mustang offers no package comparable to the Z28 because of the limited sales potential of all-out performance vehicles in today's new car market."

Ford started taking orders for the 351 H.O. as early as October 1971. According to Marti's database, the first '72 R-code was built on January 20, 1972, with production continuing through the end of the model year.

Eric stumbled across his H.O. Mach 1 when he decided to stop at Spring Carlisle during a trip to Kentucky to purchase a 60,000-mile Boss 351. "A guy was selling the car along the fence," Eric says. "When I came through the gate, I ran right over because the car was red on red. I quickly noticed that it wasn't a Boss, then realized it was a '72. Then I spotted the sign that said '17,000 original miles.' I looked at the VIN and saw it was an R-code, same as the '71 Boss 351. At first I was confused, then I remembered the H.O."

The seller was actually selling the car for the original owner in North Carolina. He had been trying to unload the Mach 1 for more than a year, having brought it to Carlisle the year before with no luck. "Nobody wanted to buy it because it wasn't a Boss," Eric relates.

Although traditional ram air wasn't part of the H.O. package, fresh air was delivered to the air cleaner through this plastic duct located under the battery.

A quick call to Bob Perkins revealed that the H.O. was really a Boss for 1972, with less than 400 built. With low production and low miles, deemed correct due to the state inspection receipts with the car, Eric made the deal for the '72 Mach 1 and returned home to Fish Kill, New York. "It saved me a trip to Kentucky," Eric says.

The car's paperwork included the original certificate of title, issued April 5, 1972, to Ernest Wicker. According to the seller, Ernest drove the car sparingly, mainly keeping it stored in his garage. Eric quickly ordered a Marti Report, which revealed that the Mach 1 was ordered on October 4, 1971, but not built until March 8, 1972. Factory options included the body-side tape stripes, rear spoiler, power steering, Rim-Blow steering wheel, Sport Deck rear seat, AM/8-track radio, console, Mach 1 Sports interior, tinted glass, and Magnum 500 wheels.

The red and black Mach 1 Sports interior is a great match for the Mach's red exterior. The shifter is a Hurst unit with a black ball.

Rarity and options aside, Eric remains impressed with the Mach 1's originality, noting that it still has its factory-installed belts, hoses, spark plug wires, and battery cables. From underneath, Eric points out the shocks with "D2" casting numbers, the paper tag on the rear axle, orange paint daubs on the back of the wheels, driveshaft markings, and the factory-installed safety wiring on the front suspension. Eric has documented everything, including the engine and carburetor tag numbers, paint daubs, and date codes. It's interesting that parts include "D1" and "D2" casting numbers.

Eric notes that the fuel pump has apparently been changed, and he's looking for an N.O.S. replacement. Also, the original mufflers had been replaced; Eric has already swapped them out with a set of N.O.S. mufflers, noting that the H.O. came with regular four-barrel exhaust manifolds, a unique H-pipe, and Boss 351-style mufflers.

Thanks to his low-mileage find at Spring Carlisle, Eric has become somewhat of an expert on '72 R-code Mustangs. He's also started a '72 H.O. registry in an effort to learn even more about these rare muscle Mustangs. If you're lucky enough to own one and would like to participate, drop Eric an email at