There are a lot of factors at play with the 6.0 and most of them are not in your favor. The engine has some design flaws, they never should have sandwiched the heads under the rocker carrier. The dissimilar expansion rates of the aluminum rocker carrier and iron head are an issue. Then there is the head bolt issue, addressed in the 6.4 by increasing the bolt size by 2mm, the bolts are not sufficient to retain the clamp load on the rocker carrier and cylinder head. Adding to the issue is the lack of fasteners, at 10 vs 17 on the 7.3 you barely have 55% of the effective clamp load.
More concerning are the under developed peripheral systems. The oil cooler is too small and poorly designed, the high pressure oil system is a collection of flawed connections in the name of manufacturing ease, and in its short production life it changed multiple times. Then there is the emissions issue. Let's face it, Navistar and Ford were spitballing here, they hoped it would work, and they were wrong. Now a lot of states are checking to make sure this equipment is present at inspection and functional, so the early bulletproof/delete philosophy is proving risky for registration and avoiding fines for deletion or deactivation.
Is a swap worth it? No. Put the truck back to stock, sell it and buy what you want. If you don't need big power, there are lots of older trucks out there that are in good shape and will get the job done just fine. Now, of the trucks to do a swap on, a 6-speed manual is by far the easiest to put any of the 5.9 or 6.7 Cummins engines in. The newer and more powerful you go, the more you'll spend though. I almost did this to my '05 but in CA it was going to prove impossible to pass inspection due to difficulties with the swap. I'll reiterate, put it back to stock, sell it, and get a different truck that won't cause you the heartache the 6.0 or a swap will.
Now, if you are going to rebuild everything, ending up with an essentially new 6.0, upgrade the EGR cooler to the BPD unit, remote mount the oil cooler, do head studs, and make sure everything is right at the machine shop. Use new Alliant injectors and replace anything that is questionable in, on, or around that engine. Break it in, put it on synthetic 10w-30, add Archoil, don't pass 5,000 miles on the oil or 15,000 on fuel filters, run the Cummins Extended Life coolant from day one, and yeah, you might have a good shot at 300K+ without problems. But that's a lot of effort on one of these trucks, weigh carefully how the money you'll spend to accomplish all that can be used towards an '05-10 with a 3-Valve V-10 or a different diesel. Just stay clear of the 6.4L PSD too, they're stupid expensive to fix when they have issues.
The Current Truck (Oct-2013 to Present):
1999 (Early) F-350 Lariat, CCLB, SRW, Black/Tan
7.3L Powerstroke, 4R100, 4x4, 3.73, 37x13.50-18s, '05 Axle Swap, 6" Fabtech lift, GTP38 "D66" turbo upgrade, SCT 4-position chip with custom tuning by me, Straight Piped 4" down pipe through 5" dual stacks, N-Fab full length triple steps, Pro-Tech cab guard and tool box, louvered 5th wheel gate, Hella 500 Fog and Driving lamps, much more to come...
The one I'll miss, (Mar-2009 to Jan-2014):
2000 Excursion XLT 4x4
6.8L V-10, 4R100, 4.30, 285/75-18, 271whp / 388wtq
The one I won't, (Jul-2005 to Sep-2012):
2005 F-350 XLT, CCLB, SRW, 4x4 FX4
6.0L PSD, ZF-6S650, 3.73, 35x12.5-18, 4.5" Lift