Ultimate Truck Performance is THE diesel shop in Southern CA. I took my 7.3 to them and was seriously impressed with their work. If I had a 6.0, it would go straight there for bulletproofing. Cost, btw, was pretty reasonable at about $4600 IIRC.
All but one mechanic at UTP drives a 6.0 with their kit (the one who doesn't has a 7.3 while he's saving up for his 6.0). I told them, "Yeah, but you guys have a shop and the experience to fix them when they break."
They said, "Yeah, but once we bulletproof them, they don't break."
6.0's do require more maintenance than other motors. In fact, if you scroll down to the 6.0 section of UJoint's FAQ page
, Chris outlines a bunch of items, including that the turbo should be removed and cleaned every 30-40K miles. So that's something to keep in mind.
I'd be curious to hear what UTP did to the transmission and why. I've always heard the 5R110 is the strong link in the 6.0 powertrain, whereas the 4R100 was the weak link in the 7.3 powertrain.
But bottom line, unless they plated that transmission in gold, I agree with Glider in post #12 and Rally in post #14. No heat, no cooktop, no propane, no rear bumper box, average winch, average fridge...that thing is way overpriced. I'd offer $69K max.