I stand by my earlier post that says the diesels come with a smaller alternator than 160 amp. The specifications you guys are reading are a blanket spec that covers both gas and diesel trucks. If you disagree, then pop your hood and take a peek at the plate on the alternator and you will see what I mean.
Also, the diesel's get different springs when plow prep equipped. Again if you disagree then check your spring #'s against my 2500 Quad Cab, plow prepped truck. My springs are drivers-986AA and pass-985AA. FWIW, I have personally checked spring #'s on 2500 non plow prep trucks and they are not the same as mine.
Finally, I draw my conclusion from the fact that I've had two '03 diesel trucks and my current '04 (all were 2500's with two being quad cabs and one being a regular cab) and all have had the plow prep package with the same smaller alternator and springs #'s.