found this on ebay, but never heard of the marker or the part before.
http://www.ebay.com/itm/Ford-7-3-6-...-glow-plug-override-switch-bypass-controller-
http://www.ebay.com/itm/Ford-7-3-6-9-IDI-diesel-truck-manual-glow-plug-override-switch-bypass-controller-/220912323972?hash=item336f668d84&item=220912323972&pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr[/URL]
http://www.ebay.com/itm/Ford-7-3-6-...-glow-plug-override-switch-bypass-controller-
http://www.ebay.com/itm/Ford-7-3-6-9-IDI-diesel-truck-manual-glow-plug-override-switch-bypass-controller-/220912323972?hash=item336f668d84&item=220912323972&pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr[/URL]