To compete with the Mopar HEMI engine in NASCAR, Ford launched the BOSS 429 V8 in 1969. It was built as a limited production Mustang Fastback to meet the required homologation of 500 units. ... They modified a version Ford's big block V8 design known as the 'Ford 385 engine' and changed the stroke from 3.85 inches to 3.59.
Origin
United Sates