I guess my question is what is the difference and how can it be identified?

 

There are a few power outputs on the 04 cummins look for a tag on the valve cover that tells you the HP of the engine. 305hp is the HO there was also a SO engine.

on the 04.5 the tag on the valve cover will say 325hp. Plus the 04.5 has a 4inch exhaust turbo back vrs 3 1/2 on the 04. The 04.5 came with a factory cat. build date for the 04.5 I believe started in January of 04

 

hell i have an 04 built in late 03 and when it was stock it had 3 1/2in turbo back with a muffler and no cat. and my motor says 305. so that means high output? and it shows exactly 32psi with a smarty. so its def not a 04.5? and is it a 600 series?

 

04 have 305hp and 555tq, 3.5in exhuast.

04.5 have 325hp 610tq, 4in exhuast.

Otherwise there the same.

 

A stock, and unflashed, 04.5 is 325HP/600TQ...610TQ was a later 05 thing. DCX did reflash the early 04.5s for "performance and mileage" (a listed TSB) and that supposedly gained you the 610TQ...but I never saw an improvement, and if anything; the truck didn't run as well after the reflashing.

And I have read where guys claimed to have a later 04 with the 305HP HO with a factory 4-inch exhaust without a cat...

The biggest identifier of a 04.5 is the engine tag showing a rating of 325HP and the presence of the large catalytic converter in front of the muffler.

 

03 and 04 have triple nickel blocks

 

Look at the build date on the b pillar. 01-04 and later are the 325\610 engines or 04.5.

Huh??? There is no difference in blocks in any of the CR's. Valves, valve seats, pistons, injectors, cams, and piston coolers are the differences depending on what motor and build date.