I've had a few cummins a
04.5 5.9 2wd auto
05 5.9 g56 6sp 4X4
05 5.9 2wd auto
06 5.9 2wd auto and never had 1 issue with any of them
I now have a 2014 6.7 with the Aisin and I would not give it up for any of my old ones.
The only way I would go gas is if I never towed anything with any weight to it.

70 duster full chassis super pro 416 CNC Indybrock heads 727 w/brake

best so far 1.212 60 6.219 in 1/8 at 110.88 9.768 at 137.81 1/4