Pretty much any square cab you like 1300, 1450 1550 although you won't get a doka but for a camper you probably don't want one. You would be looking at a good condition truck, probably with a late model engine such as the OM366LA (turbo charged, intercooled), 240 ish hp etc. You would certainly get a truck that would make a fine camper.
If you are not in a rush then waiting could be the way to go, every now and then a stellar truck shows up and not always for lots of cash. If you can wait then getting a truck in the US will be cheaper, with the exchange rate importing such a truck would not be worth it.
You should talk to Scott at expedtion imports, he gets quite a lot of later model sqaure cabs and he gives great service.
Rob