Granted they have a custom chassis, but I doubt many parts, if any, are special for them. Their production volume would not be large enough for that. What they most likely did was to purchase standard parts, that most chassis builders also use, and mount them in a position or manor that suite their design specs. Finding repair parts can be done, but you won't have the factory to fall back upon. It will become a paper chase to find the suitable part. That slows you down, but many garages will know the parts and have alternate sources to get them. I would weight that in a decision to purchase such a vehicle, but it may not stop a purchase. If I already have one, I'd plan on more preventative maintenance to minimize down time on the road. We have a similar situation with our 1989 on a John Deere Chassis, extra preventative maintenance has paid off.