Hey, I saw your ad
Just so you know, 4x4 truck campers generally cost a lot!
There are the inevitable Iveco 4010s — very good and sturdy but expensive!
The Renault B110 and B90 are very good and easy to maintain but also very expensive.
I think if you're on a tighter budget, a Saviem TP3 would be perfect for you.
Some exist in Diesel — you can find them either as a platform (on which you can mount a cargo box or caravan) or as a van, but the living space is pretty tight either way... reliable mechanics, solid Man engine...
But if you're really mechanically inclined, you could hunt for Unimog 404s (decommissioned military), but very few come in Diesel...
Hope that helps!
tom