6.4 is a nice truck, duramax have trans issues once you put power to them

 

the allison is only weak with 85hp of more added unless you add a transgo then 150 is the limit, as for the headgaskets mid year 06 they changed them to a better quality. but I have friends with the others running 2-300hp tunes and studded with no problems

 

LBz gets my vote
And the transgo is going in when I get back home