Yep the 04.5 are the 325/600 motors. The majority of trucks with build dates of 1/04 and later are 04.5s.:thumbsupCheck on the drivers side of the plastic valve cover, the one with the Cummins "C" on it, there wil be a white sticker that has various info including HP. 305 is an early 04, 325(?) is an 04.5. You can also tell by the manufacture date, but I don't know what the cut-off is.