Tom Hoover had been testing factory prototype manifolds as early as 1969 on his personal 66 HEMI powered Coronet, plus several factory mule test cars, it was slated for a late 1971 production introduction/option on the HEMI, but by May of 1970 corporate has already pulled the plug on the HEMI, with 71 being the last production year, so no new development was going to take place for RPO's