My last truck was a beautiful 2003 F-350 SC 4x4 Lariat DRW 6.0L. I absolutely loved the Super Duty truck. The engine not so much.
There was a time when it was at the Ford dealer more than in my garage. It had head gaskets replaced, one injector replaced, EGR valve replaced and more reflashes under warranty than I care to remember. Once my warranty was up I did an EGR delete to avoid some of the problems these trucks are known for and also an attempt to cure an ongoing surging problem while accelerating, which it did.
Over the next few years it developed quite a severe bedplate leak (which requires pulling the engine to repair), I had several injectors getting weak because it was running rough when cold, and the oil cooler was plugging up because my oil and coolant temps were spreading. It also had an intermittent surge at idle that nobody could ever figure out. Ford created a flash called "inductive heating" which heated up the coils in the injectors during the glow plug cycle as a low budget way to correct poor cold starts and running. The injectors were never designed to do this and ended up getting ruined from this flash which is what I'm sure is what happened with mine. Oh, and I was meticulous with maintenance on this truck; only Motorcraft filters and Delo 400 oil. The oil was changed every 3-4k miles and fuel filters every 2nd oil change.
I finally got tired of sinking money into the bottomless pit and started truck shopping 3 years ago. Most offers I had from dealers for the truck ranged from $8-10k on trade and several dealers refused to take the truck because it represented a huge liability to them with the new owner. I was never so happy when I got the deal on the truck in my signature and they took the 6.0L on trade. It sat on the lot for the better part of a year after I traded it in.
There are many diesel shops throughout the US and Canada whose existence was created by the 6.0L diesel. Also, in regards to "bulletproofing", there are too many inherent design problems with the engine to truly bulletproof them, the major one being not enough head bolts per cylinder. There are countless reports of owners having to do head gaskets over and over again even when using head studs because of this issue.
And lastly, these trucks were trouble prone right through their production run. It seems that design changes were done to correct one issue and another was created. An example of this was the change from a round EGR cooler to a square one which had a much higher failure rate. Ford spent over $1 BILLION (yes that's not a typo) on warranty work on this engine.
My advice would be to get your deposit back and shop around for another truck. If you want a Ford go with the coveted 7.3L diesel or gas, otherwise look at diesel offerings from GM or Ram.
2013 Ram 3500 Megacab DRW Laramie 4x4, 6.7L Cummins, G56, 3.73, Maximum Steel, black lthr, B&W RVK3670 hitch, Retrax, Linex, and a bunch of options incl. cargo camera
2008 Corsair Excella Platinum 34.5 CKTS fifth wheel with winter package & disc brakes