Not sure they use the mds lifters in the truck with the auto but they do help the mileage in my SRT. That would be a plus. My 06 diesel gets around 19.7 (3500 4-door) overhead is 4 mpg off. One issue after another with my truck, injectors just starting to mess up, too much electronics. I think the 6.4 would be the way to go right now, maybe the 5.7 with a longer stroke would be better but Dodge has there hands tied with emissions compliance. My 92 diesel went 200,000 and I washed it a few times. Don't they use the Allison trans now?