Folks when did the 5.9 go from the first HO to the higher HP/Torque? Was it in mid 05? What designates the higher HP ones, a # or letter in the vin?

 

If you are referring to the change from 305/555 to 325/600, that was done in model year 2004 with the latter commonly referred to as an "04.5". Some time later (not sure exactly when), Dodge decided to up their rating of the TQ to 610. I have never understood what changes might have been made to get the extra 10lb-ft. Most of us believe it was a marketing ploy when the other mfrs came out with their increased output engines.

 

I thank they add a little more timing to help put it there.

 

according to Allpar.com the 610 lb. ft. rating started with 05 models.

http://www.allpar.com/model/ram/ram-engine.html