If I didn't have a new trans in this unit, I may have considered going diesel.
You know, a duramax Allison is a great combo. Bulletproof, powerful, and it's got a good reputation in the feild. But that's an awful lot of work adapting it into an AS. The cummins is simple Don't know if you can put an Allison on it, but that would be a great combo. I had a cummins in my dodge. It finally was broke in at 38 K miles. 18.7 mpg .
Are you happy with your gear vender overdrive. I'd be interested in it, if your looking to sell..
The only real advantage I can see going diesel is the mileage, and longevity. They use twice the oil, they re louder, fuel price is pretty close to gas, and they're a lot more expensive to fix. The cool factor does come into play here,
If I had a line on a cummins Allison combo, and had to do what I did with my AS, I may very well have gone diesel. It's a toss up. But I love diesals, the sound, the smell of the smoke, Rollin coal is very cool. DJ