Mile Marker 95-32721 Conversion Nut Kit 1 ton use Use with a Mile Marker 449S/S 1 ton use Use with a Mile Marker 449S/S NOTE: The kit is required on Ford super duty trucks prior to model year 1999 that have an in cab controlled 4WD Vacuum system. If the truck already has factory manual lock-outs or after market manual lock-out, the conversion kit is not needed.