Speaking as a former Ford parts salesman, those part numbers are not the full part number, but just the basic or group part number. Example camshafts are 6250 and mufflers are 5230. For a complete Ford part number you need the prefix and the suffix. Example C1AZ-6731-A if I remember correctly is an FL-1A Motorcraft oil filter. Motorcraft part numbers are different than actual Ford part numbers. To order the engine heater you either need the accessory kit part number or the full part number of all the required parts. Hope this helps.
Check your build sheet if you purchased new, or look it up by your VIN. It comes from the factory for the cold states, it may be wrapped up under your truck.I just picked up my Ecoboost a few weeks back. I tried to order it with an engine heater, but the dealer said it was not available. Any recommendations on where to get a good engine heater?