The problem with plowing money into the 6.0 is that it is still a 6.no in the eyes of a buyer, which diminishes the value of the truck relative to anything else. That may be ok with you but it should be considered in your decision, especially if you ever plan to sell.
Not in my eyes, I'll take a chance on a 6.0Llong before the 6.4L. If the seller has documentation for a properly upgraded 6.0, it's worth a look and maybe a little extra money. When I was looking to upgrade from a regular cab 7.3L to a crew cab diesel I combed through a ton of 6.0 pickups. As long as stuff is well documented I'd not hesitate in the least if it was the pickup I wanted.
A lot were supposedly bulletproofed, but no documentation and I wasn't willing to take a chance. Really I was looking for a stock 6.0 to upgrade. However, I never found one that wasn't "bulletproofed" or running a tuner. Tuners really were the biggest issue, when you don't have a clue as to which tune was enjoyed the most.
Wound up going with an 06 LBZ Duramax, don't regret it in the least when it comes to the engine, transmission, or ride. The truck has some other minor issues that annoy, but aren't serious. It pulls better than my old 7.3L and fits the whole family.
