I have an '06 6.0 Superduty with 165k on the odometer. I pull 11-12k lbs on a daily basis. With this weather we have been having (day after day of 100*+ temps) it has been running tremendously hot (I've seen 207* on my gauges). I know it is in dire need of studs, gaskets, oil cooler, EGR delete, etc. I've put 90k miles on it since I bought it 3 years ago and I still owe $19k on it.
So my question is this, should I:
A- Drop the money on this truck to Bulletproof it and stud it and probably end up putting a tranny in it along with whatever else needs to be done to make it reliable?
B- Buy a gently used 6.4 and have the power and shift-on-the-fly capability of the H&S system?
C- Buy a brand new 6.7?
First, relax. 207* is perfectly fine for a diesel (especially if towing) and it probably is happier there than at 190*. The important question is what is the temp delta between the coolant temp and oil temp. That is extremely important to know as that's how you monitor the health of the oil cooler.
Delete the egr if you can. If you can't get a Bulletproof Diesel egr cooler. Flush the cooling system real good and replace the Ford coolant with a Cat EC-1 rated ELC coolant. Do that and you will have gone a long way toward fixing the reliability issues of the 6.0. Other things that are known to be failure points are the FICM, the STC fitting on the HPOP, Dummy plug and standpipe o-rings on the HPO system. An edge Insight CTS or CS will let you monitor all of that stuff so you can see a problem developing and deal with it before it leaves you stranded somewhere.
I wouldn't bother pulling the heads off unless the head gaskets go. If that happens, stud it, use the stock Ford head gaskets, and take the heads to a machine shop to make sure there are straight, no cracks etc. Have bronze valve guides and hardened valve seats installed and the max that can be shaved off the deck to square them up is .008".
All the issues and fixes for the 6.0 are well known and documented at this point. I wouldn't trade mine for a 6.4 or a 6.7. If you are willing and capable of doing your own work everything I suggested can be done for about $1000.