Wow! This is so entertaining. Seems everyone can rationalize their choices. Probably a good thing. I think the OP probably needs to have his truck checked out by a good mechanic or perhaps his expectations climbing mountain grades may need tempering. One thing for sure, his make and model has been proven exceptionally capable.
Regarding gas vs. diesel and 1/2 ton vs. 3/4 or 1 ton, all have tradeoffs.
My previous truck was a '99 F350 with diesel. Great truck, with zero engine issues, good fuel mileage. Everything else though was more expensive with a HD truck. Brakes, transfer cases, oil changes, so maintained things I could myself. Paid about $35K new and got $10K on trade last year when I bought a new 1/2 ton. It had 190+K on the clock. 235 hp and 500 lbs. of torque. New ones have twice the power and torque and cost twice as much. They are also twice more complicated, laden with emission systems and while I cannot speak to the present generation, the ones that followed my 7.3 had many issues that affected reliability, economy and longevity. At least the Fords I have read about. Diesels with their power and HDs with their payload capacity are awesome at towing. If you feel the need, go for it.
I do not miss the unloaded rough ride and the noise, but the 6 spd. bullet proof manual will be missed. From day one the fuel cost premium for diesel was significant, but that's part of the price of admission.
New truck is F150 with gas V8 and is quite luxurious and car like. Very comfortable indeed. 385 hp./387 torque, 2031 payload and 9100 lbs. max tow. So far, so good towing 25FC and getting about 11-12 mpg in the NW Georgia hills and south to Florida. 17 unloaded on the backroads where I live and 21 on the interstate. Definitely feel the AS behind the truck but very stable. Will be interesting to see how well it does this August in the real mountains of Wyoming, Colorado and Montana. Can't wait and wish me luck!