Do think you are incorrect on Duramax, as Chevrolet/GMC (discounting the ill fated Oldsmobile used in a few half ton trucks) 1st started with the 6.2 liter, putting turbos on some of the 6.2's. then went to the 6.5 (~same block) with the 6.5 TD. I special ordered a NON TURBO 6.5 diesel in my 1994 1/2 ton. It is the only non-turbo diesel that I know of.
The Duramax name came out ~1999 and was a 6.6 liter and was a totally different block. Yes, Cummins builds a GR8 diesel. Maybe Caterpillar is better, but the new RAMS are otherwise 60,000 mile trucks. FCM should merge with Yugo.
Even Google is not very accurate in their years, etc. but soon the Chinese will be competing with Google and probably doing better.