The Ford Boss 429 was developed for NASCAR it was Fords Answer to the Chrysler Hemi. They shoehorned the BOSS motor in the 1969 and 1970 Mustang and it really wasn’t the monster on the street the owners hoped it would be. You were literally getting a detuned race motor for the street. But never the less a few individuals put their heads together and came up with a few tweaks and solutions and the end result was the Hemi Killer on the street they had hoped it would be.