If Semon "Bunkie" Knudsen hadn't left General Motors to join Ford Motor Company in 1968, chances are there never would have been a Boss 429 Mustang. Knudsen had risen through the ranks at GM, first as general manager of the wildly successful Pontiac Division, then as head of Chevrolet Division. Knudsen was a proponent of racing and high performance, and that philosophy had resulted in a long string of Pontiac and Chevrolet muscle cars.
His successful stewardship of these two GM divisions rewarded him with a promotion upward into the corporation's top management ranks and what seemed like the fast track to the position of General Motors president. Knudsen would ultimately lose that battle to Ed Cole, and he wasn't happy with the GM board's decision. Henry Ford II felt Knudsen was the perfect man to inject some of the GM product and marketing philosophy into Ford. Over internal opposition, Henry Ford II offered Knudsen the top job at Ford. Knudsen cut his lifelong ties with GM and moved across town to the Blue Oval.
One of Knudsen's first moves was to put more muscle in the Mustang lineup. Ford had owned the ponycar market for the first four years it was on the market, but by 1968, the Camaro and Firebird were mauling the Mustang on the street with bigger-displacement engines. And in the SCCA's fast-emerging Trans-Am racing series, the Camaro Z28 was sticking it big time to the Mustang. Knudsen understood that both the Trans-Am series and the Mustang's lack of street performance cred were undercutting the brand's sales and image.
Knudsen immediately ordered Ford engineering and design staffs to conjure up a Z28-style Mustang. "Ford had the Mustang," Knudsen told author Donald Farr some years later, "which was certainly a good-looking automobile. There was nothing wrong with it, but there was a tremendous amount of people out there who wanted a good-looking automobile with performance. If a car looks like it's going fast and it doesn't, people get turned off. I think if you have a performance car and it looks like a pretty sleek automobile, then you should give the sports-minded fellow--the car buff--the opportunity to buy a high-performance automobile."
The result of this new Ford philosophy was the Boss 302 Mustang. Styled by Larry Shinoda, the GM styling wunderkind who had followed Knudsen over to Ford from Chevrolet, the Boss 302 looked the part thanks to its special stripes, big spoilers, and a radical new 290hp 302ci engine, identical in specs to the Z28.
Because of the modifications needed, Ford chose to outsource the Boss 302's suspension changes to Kar Kraft in Brighton, Michigan. Ford had turned to Kar Kraft in the past for special builds; they had been responsible for the construction of the GT40s that went on to win LeMans. While working on the Boss 302's underpinnings, Kar Kraft was also tapped to build what would eventually be called the Boss 429 Mustang. Knudsen was a strong supporter of stock car racing, and felt it necessary that Ford return to NASCAR dominance. He had a new race engine, the "Semi-Hemi" Boss 429, and he needed to make it legal in a hurry.
Thus, the Boss 429 Mustang was produced for one reason, and one reason only: to homologate Ford's new engine for NASCAR competition. Ford was still struggling to compete with Chrysler's 426ci Hemi, and the new "Blue Crescent" Boss 429 had all the earmarks of taking the game right back to Dodge and Plymouth. Based on a beefed, high-strength version of the production 429ci cast-iron block, the Boss 429 had four-bolt mains, a forged steel crank, massive forged steel connecting rods, and forged aluminum pop-up pistons with 10.5:1 compression for street use.