The PMD is a problem area, but can be resolved by getting it out of the engine bay and either in the front bumper, or moving inside the cab with an extension cable and cooling plate.
Timing chain, dont go the gear drive method, great for the newer engines, but not the 6.5. The 6.5 timing chain is usable to 1in of play, and even more. There is too much backlash of the valvetrain at decel for a gear drive, some have been known to break the cam or IP drive gears.
Fluid Damper has just released a new damper this year that addresses the harmonic balancer issues on these trucks. I would recomend one of those as I have seen rave reviews of them and most are commenting how the trucks now idle like a gasser.
Tony