I've been kicking around the idea for awhile of building a 1985-86 250 super-motard (using that era engine bodywork, tank, seat, etc) and want to make it street legal. What years were the old 610's street legal using those frames?? Can a 2-stroke engine from mid 80's still bolt right into the last of the original left kicker style 610 frames?? Dreaming I know...