No clue on the idling speed problem. The clutch is what I call a Reeves drive, it is used on some woodworking and metal shop equipment. No experience with that one, but you have to "calibrate" new ones. With the engine change out, and a used belt that has stretched over tome you might have to figure out how to "calibrate" the clutch.
Combat Infantryman, the ultimate hunter where the prey shoots back.
_____________"Illegitimus non carborundum est"_______________