1948 "Paleface Special" and "Emperor Waltz" with Wally Parks between the racers, they are both named for movies that Hope and Crosby released in the theaters that year.
If it had wheels, Wally Parks was interested in it, and these downhill racers were supported by the Hot Rod Magazine and NHRA in early Soapbox Derby programs sponsored by Chevrolet.
Sidenote, celebrities used to go to the National Soapbox Derby, and a list of them is at http://www.soapboxderby.org/aasbd-race-program/history/celebrities.aspx but after the 80s, the star power isn't there at all. I just don't even recognize the names. But back in the 40s and 50s some major celebs showed up, Ron Reagan, Jimmy Stewart, Eddie Rickenbacker, Dizzy Dean, jack Dempsey, General Doolittle, Roy Rodgers, Abbott and Costello, Art Carney, Glenn Ford, the cast of Bonanza, Fess Parker, astronauts Lovell, Ward, and Gordon, Peter Fonda, Evel Knievel, and many others.