The Boss 429 was a high performance Ford Mustang variant

Ford Mustang variants

Ford and several third party companies offered many modified versions of the highly popular Mustang in order to cater to specific portions of the marketplace outside of the mainstream...

 offered in 1969 and 1970.
The Boss 429 is arguably one of the rarest and most valued muscle car

Muscle car

Muscle car is a term used to refer to a variety of high-performance automobiles. The Merriam-Webster dictionary defines muscle cars as "any of a group of American-made 2-door sports coupes with powerful engines designed for high-performance driving." Usually, a large V8 engine is fitted in a...

s 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

Ford Motor Company

Ford Motor Company is an American multinational automaker based in Dearborn, Michigan, a suburb of Detroit. The automaker was founded by Henry Ford and incorporated on June 16, 1903. In addition to the Ford and Lincoln brands, Ford also owns a small stake in Mazda in Japan and Aston Martin in the UK...

 was seeking to develop a Hemi engine

Hemi engine

A Hemi engine is an internal combustion engine in which the roof of each cylinder's combustion chambers is of hemispherical form.- History :...

 that could compete with the famed 426 Hemi from Chrysler

Chrysler

Chrysler Group LLC is a multinational automaker headquartered in Auburn Hills, Michigan, USA. Chrysler was first organized as the Chrysler Corporation in 1925....

 in NASCAR's Sprint Cup Series (then known as "Grand National Division").