Ford 351W Street Pro-Billet Small Diameter Distributor For 351W, Includes Iron Gear And Vacuum Advance. Must Be Used With An 6, 7 Or 8-Series MSD IgnitionMSD engineers fit all of their high performance distributor experience into a special compact housing designed to be less obtrusive for Ford engines. The diameter of the special cap and housing are 5 8 Inch smaller than stock Ford distributors providing extra room in front of the engine. The new MSD cap features spark plug style terminals and is firmly screwed down to the housing. The distributor relies on MSD's race proven magnetic pickup and