The Boss 429 is arguably one of the rarest and most valued muscle cars to date. In total there were 859 original Boss 429s made. The origin of the Boss 429 comes about as a result of NASCAR. Ford was seeking to develop a Hemi engine that could compete with the famed 426 Hemi from Chrysler in NASCAR's Sprint Cup Series (then known as "Grand National Division"). NASCAR's homologation rules required that at least 500 cars be fitted with this motor and sold to the general public.