The Bobbable and crew cab conversion might be a problem. Most bobbers have the frame length cut down. Once you do that you have a smaller bed. Then converting it to crew cab might make the bed too small to be a worthwhile project. But if you were going for an "Avalanche" type vehicle then full speed ahead. Given this I would say a deuce ( 2 1/2 ton) cargo truck would be a good choice. I would look for one with a multi fuel engine, winch, air shift transfer case for 6 wheel drive, as you are in Oregon and winters get frosty you might also look for an ether start assist or at least has not had the start preheat deleted. South of the Mason Dixon they tend to not need a lot of help starting in the winter. The deuce usually comes with non directional / cross country tires in a 9.00 - 20 size. total tire height is then 38 inches. it will run 11.00 - 20's fairly well. you can get quite a variety of tread patterns in that size. depending on what type off roading and on roading you plan to do. Larger tires than that have advantages but come with some serious drawbacks as well. The standard split ring rims are very serviceable and one man can handle them along with the 11.00 - 20 tires. bigger than this, the weights get pretty serious and can be costly. plus where and how to keep a spare? there are some other rim solutions that do away with the split rings. again if cost is no object feel free to accessorize. If you are going to cut the frame down and crew cab it then you probably don't need a deuce that still has its stakes, bows and canvas cover over the bed.
Regarding the truck speed and tow capacity. The more weight you tow/carry the more you will slow down on hills. Much more so than if you were in say an F250 diesel. However, because of its weight and low end torque the deuce would win a tug of war. That being said, bigger tires and wheels( rotating mass) under a hard load will help you find any weak spots in the trucks drivetrain and brake system. Like most vehicles, as originally designed and built, they do there assigned task in an acceptable manner. Its when we start tinkering with them that we find a change here and there requires beefing something else up. Usually we don't find that out until something goes into catastrophic failure mode. The m35a2 has a multi fuel and the m35a3 has a big cat engine and is singled out. auto tranny as I recall. so it has some advantages in that area. I have heard the big cats are expensive to work on relatively speaking.
The central tire inflation thing always sounds good on paper, but my experience has been they are problematic unless you are very diligent about servicing all the components. every o ring, valve, control circuit, rims, etc etc. Remember, the split ring rims have an innertube. if you flat out it might be possible to replace/repair the tube and be on your way. tubeless tires might not be so easily put back on the road. although you can slime tubeless tires. As the deuce has on board air and easily accessible fittings, perhaps a hose and tire fill valve are more than adequate for most people that like to air down and air back up. That air also comes in handy for air powered tools should you need to take apart something that is torqued down to five jillion ft pds or you don't have a cheater bar long enough
my two cents.