I'm sure that's what my truck is gunna need I just can't find it in the specs anywhere. They upgraded to 20mm in 05 right?

 

January of 06. Yes, you'll need 18mm gaskets for your 04 if the motor is original.

 

I have been seeing that if there are 8 bolts on the outside of the bed plate fastened into the block,, all I have seen like that are 18's. And all of the ones without the 8 bolts have been 20's. I've been watching so I can know before tearing into them. This should tell you which ones you have just by visual inspection.

 

Call a Ford parts department with the VIN number and they can tell you.