1) Stock engine must be retained, but may be replaced with any available in
make/model/year. Any and all modifications are permitted, with the following limitations and exceptions: Stock engine-block must be retained, as originally manufactured (boring, stroking and other internal engine modifications are all permitted). Forced-induction of all types is not permitted, unless factory-equipped.
2) If equipped with a water-cooled engine, the radiator must remain within 6" (150mm) of the original location, as originally manufactured