2004 Models: If you have a 2004 model you must check your VIN code to determine your production date.

The 2003 front engine cover is no longer available. In the even your front engine cover was replace, it was most likely changed to a 2004.5 cover in which there should be a Ford giving a sticker that the housing was updated. 

A sample VIN code is: 1FTRW21P24EB10150. In the middle of the VIN code, you see the digits "4EB". The 4 means that it was a 2004 model year. The "E" denotes which production plant built your truck. In this case, E is for Kentucky. Lastly, the "B" is the start of the sequence number (the last 6 digits of the VIN). Some early 2004 models have a "4EA" code. The "A" denotes the early build and most likely is a 2003-2004.25 production date. For example letter "B", "C", "D" or more all denote later model 2004 builds with 2004.25 and newer production dates, or if the water pump is already off the truck you can measure the impeller.