I don't have the service manual for the 2004, but decided to check the 2002 just for the heck of it. The service manual would imply that you may need to add a tensioner if you replace the belt. The water pump and drive pulleys look the same on the 2002, but mounted to the round location halfway between the two pulleys is a tensioner. In the instructions, the manual states:
Accessory Drive Belt Tensioner —Water Pump, 3.0L (4V)
Removal and Installation - NOTE: If equipped with belt tensioner.
Remove the water pump belt. For additional information, refer to Water Pump Belt—3.0L (4V) in this section.
- Remove the bolt and the belt tensioner.
- To install, reverse the removal procedure.
It appears that a tensioner could be bolted on to your engine as well, then it would look exactly like the 2002.
-Rod