I can speak with at least some authority on Van Hool wheels, since I now have eight of them on my Neoplan.
Your wheels are European-spec -- 335mm bolt circle. They are hub piloted wheels. So, for starters, the vast majority of wheels available in the US, and especially on eBay, will not fit your coach.
The next issue is whether or not you are replacing steel with aluminum. If so, you probably do not have enough stud length to make a straight swap -- the aluminum wheels are thicker. In this case, you have two choices. One is to replace all 60 studs with longer items. The amount of extra length you need on the drivers will be double what you need on the other 40, unless you use steel inners.
The other choice you have is to go with a special, retrofit wheel. This wheel, available from Alcoa and I think, also, Accuride, has extra-large lug holes. You then use a special flange-nut that has a sleeve which reaches down through the extra-large lug hole to secure the wheel to the existing stud threads. I think you may find that the special wheel (which is only a tad more expensive than the standard ones) along with the special sleeved nuts is less money than hammering out and replacing all 60 studs. If you go this route, you will only be able to use aluminum wheels on the outer drivers -- the inners will need to remain steel. This is the configuration we went with. Lots more about our big wheel adventure in our blog archives from last March, here: http://ourodyssey.blogspot.com/2005_03_01_ourodyssey_archive.html
I do have all the Alcoa and Van Hool part numbers for these wheels, someplace. If you need the numbers, or more advice, or just want to talk to someone else who has been through the weird-Eurpoean-wheel nightmare, call me on cell at 408-892-6227.