All of the above.
For an illustration of the freehub bodies, check
here
And for parts, well it's true that it is hard to find. Most Campy distributors will stock 8-speed cassettes however, so grab a few while you can. The only other critical part might be the rear derailleur. You can always overhaul the shifters. Can you use 10-9 speed front derailleur and chainrings on 8 speed?
8 and early 9 sp derailleurs are getting so hard and expensive to find. Supposedly, Jtek #1 will allow you to use a 10 sp der with your 8 sp setup. I personally haven't tried it. I did hear this directly from Jtek though. They said they don't publish it for some reason. Go figure.
Tim