They certainly have a cult following. They're good motors. The salesmen used to pontificate on why air cooled motors were superior to liquid cooled motors with the related corrosion and such. The horror stories they'd spin about water pumps, sludge and frost. Deutz has now moved on to building liquid cooled diesels. I wonder if the salesmen still use the same salespitch?
Here's a link to some parts suppliers. Maybe you'd want to give them a call to see if they know what they're doing or if they're just a name on a list: