Same old problems with the 6.4 as any other diesel in a ford. They are pretty known for turbo problems, injectors, plus its a ford. Ive heard of the turbos going out within a few thousand miles of new and seems to be a pretty common thing. Personally i think it would be a huge step down from your duramax, every 6.4 ive rode in is real sluggish for a twin turbo, plus being an 08 you have the emission crap. Basically all you get that is better is a solid axle. But with your chevy you get reliability, good ride, better creature comforts, and i think just as much power or more. Throw twins, some cp3 work, studs, and tranny work and you will have a bad ride that no ford will ever touch in any way.
Ive been watching some of the built 6.4's at drags and pulls and they are pretty fast rides. Rudy's diesel is building some and they are fast but are proving time and time again to be very unreliable. Every one he has personally built has been in the 800hp range (drag trucks) has not lasted basically past its first day at the track. Now i know your not doing anywhere near that but just look at the built duramax's that are at that hp (look up a guy by thename of dimitri milard and check out the d max's he builds), they are much more reliable at that hp so you know they will hold up much better to your 400hp on the street.
