I'll start off saying I don't think I have set up my engines any different than anyone else. I used Heath diesel injectors, pcm and water injections.

First engine was the original stock engine that came in the suburban. The number eight cylinder cracked which from my understanding was a know defect.

Engine (2005 GEP long block) two was went down from cracked main webs. Engine (2008 GEP long block) went down due to broken crank, main caps and cracked main webs.

The vehicle is used in vacations which are usually in the mountains.

Still have the original 4L80E transmission and 14 bolt semi float rear end.

So after 8 months going back and forth with GM I decided to do a engine conversion with a cummins.

14 weeks later I can not be more happier in doing this. With 21mpg plus and more power than a 6.5 would dream of in comparison I say I did the right thing.

Here are my thoughts.
The 12v is not as fast (but very close) acceleration. Maybe with a little more work on setting up the shift points on the tranny to match the low torque would help.
The 12v VE engine is more quiet than the 6.5. Starts way easier than the 6.5, in any temp(engine hot or cold)
Better fuel mileage towing or empty.
Here is my set up.
12v VE Cummins, Bosch 175hp injectors (15hp over stock) Stock VE pump, 98 Cummins inter-cooler, 02 Dodge Cummins radiator, Fass fuel system, Hy35w turbo 3" down pipe to 3.5" exhaust, straight through muffler