Stephan - I've driven all over in a modded FJC (and FJ7Xs, LC200s, etc.), including to Khartoum, Somaliland, etc. Are there security issues? Sure. But there are also security issues if you plan to drive through Detroit or Istanbul or London.
I think one major misconception in your question that I feel obligated to address as an economist is that poverty does not cause violence. In fact, there is very little empirical evidence over the past decades and centuries that poverty alone actually raises the amount of violence in a given population. And this is even more true in Africa, where many of the poorest parts of society are also the most peaceful. Normative decisionmaking and exogenous factors have far more of an influence than poverty, and we see this from Popkin's work (The Rational Peasant) up through Douglass North and even Mary Kaldor's recent work on insurgencies, terrorism, and new wars. The motivations for violence are complex, which Locke and other philosophers recognised - a breach of the peace, or a breach of the social contract (a prevailing normative arrangement), requires motivation that is beyond simple poverty for the vast majority of people.
I realise my perception of these things may be different, as I live in Africa full-time. Yes, I travel and keep an office in London and one in the States, but northern Uganda is my primary residence. My neighbours are Ugandans who live in mud huts and greet me in Acholi in the morning. I speak Acholi (or Lango) when I go to the market to buy things for dinner or to buy a chicken to slaughter. Most people I know here (I am writing this this near Yoo Kitgum, in northern Uganda) are poor farmers, and the average income in my village (which is a place of substantial size - over ten thousand residents, plus a large UN/IDP camp containing hundreds of refugees) is under $3/day. Many people I know here make less than $1.50 per day, after ten or twelve hours of back-breaking physical labour.
Parking a "nice" truck here is like if someone parked a really nice spaceship in your neighbourhood; it's so outside your realm of understanding that you wouldn't know the difference between it and the Dodge Neon of spaceships. But one advantage of the retromod thing is that checkpoint guards, customs/border agents, and others do notice or approximate the age of vehicles and will, for instance, ask for a lower bribe from a 109 Series truck than a brand new Defender. That said, if I have knowledge of the local language - or even sometimes if I don't - the bribe often has more to do with negotiation finesse than what you're driving.
If you're talking about theft, theft is not an issue. If it were stolen, no one in these regions knows anyone with money to sell a stolen vehicle to. In fact, no one knows anyone with enough money to even buy fuel to get the truck away from the scene of the crime.
Also, property crimes are taken very seriously in this part of the world (much more seriously than anywhere in World One), in part due to the lack of a court system. I was once at the Maco Dwogo (means "the fire returns" in Lango... maybe I'll post about the history of that market and its name sometime in another thread...) market, a major trading market that occurs on Thursdays in Oyam. A young man of maybe sixteen or seventeen years old was accused of attempted theft of a goat. That's right, attempted theft - everyone agreed that, even if he had tried to take a goat, he hadn't succeeded. The goat in question was happily residing on the side of the road, next to its owner's little stand where she was trying to sell peppers and tomatoes from her garden (the goat was likely 80% of her net worth). But, within twenty minutes, men had moved in and cornered the man. Once he was on the ground, younger men moved in with bricks and cinderblocks, quickly turning the "defendant" 's skull to ketchup, much to the approval of the mob. The goat involved in this dispute was worth about a tenth of one of the KM2 tires on my truck, so I don't need to explain to you what would happen if you committed a theft of a larger size. Your hut would be surrounded at night while it was set on fire and the mob would make sure you and your family were incinerated. Or, if that didn't work, an informal firing squad would be convened at the local football pitch the next morning - sadly, a nearby village has a football pitch that is even named Pingh Aneko (means "the ground for killing/butchering" in Acholi), due to this dual purpose.
Lastly, you shouldn't own anything that you have to actively worry about or that tames your will to have an adventure. Things are nice, but they are only things. If it's stolen, destroyed, etc. I can have another one built, or build another project, or whatever. A friend of mine, who lived in Sudan for a long time, recently went to a wedding in London wearing one of the most abused Rolex Sea Dwellers in existence. He has the movement maintenance done on it and so on, but the case looks like it's been subjected to crash testing. Another guest at the wedding noted the condition of his watch and asked why he would treat it so badly. He replied, "Some things are engineered to have hard lives and survive." I guess I feel the same way about Toyota trucks. I think of the advice given to many Japanese soldiers during WWII: "Don't stop because you are in pain. Don't stop because you are bleeding. Stop only when you are satisfied that you can die with honour." I think this applies, too, to well-made products - a good truck, a good watch, a good pistol, a good piece of luggage, won't stop working because it has suffered some aesthetic imperfection, and it will sacrifice itself to get the job done.