In the late 1960s and early 1970s, Nascar was in its golden age. Automakers took the business of stock-car racing seriously and would dream up engines and bodywork for racing that were often too wild for the street. All the automakers needed to do was sell 500 of these radical cars and they could run them in Nascar.
The Boss 429 Mustang was just such a beast. Although the Mustang didn't compete in Nascar, the 375-hp 429-cubic-inch V-8 under its hood was designed specifically for racing and built to rev to 6000 rpm. The problem was, this motor did not perform well on the street. It was slower than the other big-block Mustangs at the time. The Nascar-bound V-8 was monstrously large and did not fit in a stock Mustang's engine bay. So Ford contracted Kar Kraft in Brighton, Mich., to handle the job. The company relocated the shock towers, widened the track of the front end using unique componentry, relocated the battery to the trunk, and fitted a smaller brake booster—all to make room for this beastly powerplant to fit in the Mustang. Today, the rarity and mystique behind the Boss 429 has pushed values at auction well beyond $200,000.
Little-Known Fact: There were actually three different 429 engines installed in the Boss 429 between '69 and '70. The hardcore "S-Code" was installed in early cars and filled with race-duty parts. But the S-Code had warranty problems, reportedly because of an incorrect assembly process. So the "T-Code" with lighter-duty parts was used in some cars. The later "A-Code" version of the 429, equipped with smog equipment and a new valvetrain, appeared toward the end of production.