I know there restrictions on size and weight when you travel in Europe. Are you sure you want something so big? I have a Host Mammoth on a Ram 5500 but would choose something different to travel in your part of the world.
If you are looking at these large campers a 3500 DRW is the minimum truck you will safely need and you may need a bigger one based on how the ratings converted over in Germany. In addition to the Lance model you seek, Northstar makes a big camper with no slides, Arctic Fox makes a large 1-slide camper, Adventurer makes a large 2-slide camper, Eagle Cap makes large 2 and 3 slide campers and Host makes large 2 and 3 slide campers. These campers will be 8-8.5' wide and 12-13.5' tall when placed on the truck. Expect the weight of the camper and truck to exceed 12,000 lbs for the lightest combination and 18,000 lbs for the heaviest.