The Facebook post from Gateway Classic Mustang only said, "Check out what rolled into the shop today." There were no other details, just a photo of a yellow '69 Mustang SportsRoof that looked very much like the Boss 429-based Quarter Horse concepts from 1970. A call to Jason Childress at Gateway was in order.
Through Jason, we learned that the Shelby-like Mustang was none other than the Boss Snake, designed by Kaucher Kustoms and built by RPM Hot Rods as the Goodguys Rod and Custom Association's 2010 Grand Prize Giveaway. Powered by a Jon Kaase Boss 429, the Boss Snake was won by Tom Ramsey during the Southwest Nationals in Scottsdale, Arizona. He drove it home to Hazelwood, Missouri, and was visiting the Gateway shop near St. Louis for some minor upkeep when Jason snapped a photo for Facebook.
The Boss Snake was conceived by Goodguys as a modern version of the Quarter Horse prototypes built by Kar Kraft in late 1969 as a possible replacement for the Shelby and Boss 429 Mustangs. Two were created from actual Boss 429s, one in Candyapple Red and the other in Grabber Blue. At Ford, they were called the "Composite Mustangs" because they used parts from a variety of Fords, including the Boss 429 body and chassis, Shelby fiberglass front end, and Cougar instrument panel. With economy replacing performance in the early 1970s, the Quarter Horse idea was shelved. Both prototypes survive today in collections.
Goodguys looked to the original Quarter Horses as inspiration for their giveaway Boss Snake. But in Goodguys street-rod tradition, they wanted a modern rendition with an updated engine, suspension, and interior. Kaucher Kustoms was then commissioned to sketch the design before turning the project over to RPM Hot Rods near Pittsburgh.
Instead of starting with a vintage body, RPM took the clean-sheet route by basing the project build on Dynacorn's '69 Mustang body shell, although RPM eventually purchased a '69 Mustang parts car as a donor for the smaller bits and pieces. With the Shelby fiberglass front-end ordered, RPM massaged the Dynacorn sheetmetal by hand-fabricating scoops in the rear quarter panels, installing rear wheel tubs, and widening the rear fenders slightly for the custom Intro wheels and BFG P335/30ZR18 package. Volker Auto Body in Youngwood, Pennsylvania sprayed the unique "Goodguys Yellow" paint from PPG.
Of course, in 1969, Kar Kraft modified the Mustang's shock towers to fit the wide Boss 429 engine. RPM performed a similar task by cutting out the Dynacorn towers and fabricating new ones to accommodate the hemi heads. The firewall was also moved rearward by four inches so the engine could be positioned four inches further back for improved weight distribution.
The suspension is a combination of RideTech's ShockWave adjustable system adapted to the Mustang with Alston Chassisworks components. Baer 6-piston brakes with 14-inch rotors bring the Boss Snake to a stop.
Because the Dynacorn body shells don't include an instrument panel, RPM was free to fabricate their own, sticking with the Quarter Horse's Cougar shape but adding Classic Instrument gauges, Clarion/Kicker sound system with navigation, and Vintage Air climate control. RPM also custom-built the console and installed RideTech's new Tiger Cage before upholstering everything in black leather from Finish Line Interior.
And then there's the engine. Not wanting to use "just any" Boss 429, RPM approached well-known Ford engine builder Jon Kaase, who recommended one of his 520 cubic-inch strokers based on the production 460 block. With a Comp Cams' hydraulic roller camshaft and custom headers, the big Boss makes 771 horsepower and 501 lb-ft of torque. From there, a Centerforce clutch sends the rotation to a Tremec 6-speed transmission and Currie 9-inch rearend with 3.89:1 gears and 35-spline axles. At the Scottsdale Goodguys, Ramsey was selected as one of the finalists with a chance to win the Boss Snake.
According to witnesses, Ramsey yelled, "Yippeeee! I'm driving it back to St. Louis!" when his lucky key fired up the Boss 429.