While I like pickup trucks for various uses, They are not well suited for full time overland travel. Mostly due to the extra weight and reduced space created by the bed, and the long hood eating interior space. You are saddled with an unnecessary leftover from the trucks previous life with the bed. Ditch the bed and go with a camper that replaces it if at all possible.
Before you decide on the vehicle to buy, I strongly suggest you rent/borrow a few different options. A compact class C/B, truck-bed camper, campervan, anything else that suits your fancy. I see way to many folks jump into the full time travel life. They pick whatever vehicle first caught their imagination. Be it #vanlife, #trucklife, or just a wrangler with a RTT. Often they find themselves limited by their initial impulse choice. Either by space, weight , reliability, capability. Given you may put a year of hard daily work into a custom overland camper, this is not something you should trust your gut on. Open your horizons (if they are not already open), and work through the gambit of options.
Look at what current overlanders are using successfully long term. People spending less than 6 months on the road, and those with a stick-house home base generally don't count. There is a huge difference between semi-full time, and true international overlanding. Search for honest unvarnished reports (NOT influencers). These types of reports include the good and the bad in an objective manner.
Most long term travelers in this category opt for vehicles that have the most usable floor space, while balancing exterior footprint. You will not see many pickup trucks (there are some folks who use the platform, such as
@locrwln, see his build thread).
Don't be lured by the "Exponess" of a vehicle. Everyone seems to want a big 4x4 on 40" tires. One with the widest stance, biggest bumpers, and heaviest "armor". The truth is you will definitely avoid dragging your home across 200 miles of brutal washboard if possible. You won't be driving technical trails, and 95%+ of your driving will probably be on maintained roads. The truth is you may not even even need 4x4!
Instead of sacrificing heavily in many areas of comfort, storage, fuel economy, etc. Many opt to use a modest size commercially produced RV. Add a carrier and a small motorcycle. The moto will take you places you would never take a car/truck/RV. While many folks try very hard to find empty car-camping, I find that the best spots are found backpacking/hiking. Nothing deters the seething tourist hordes like a 5 miles trek.
As far as vehicle parts go, in wide reaching travels, you will inevitably be the mechanic, or at least by the one advising the local. Parts will have to be shipped air mail. Even if you find a XXXX dealer in another country, they may not have access to the parts you need, or even know what your engine type is.