I drew up a Water Cooled Puch E50 head in 123d Design. I printed it out with a 3d printer with low infill. This will allow it to be flask casted with aluminum. The holes were slightly smaller so that the spark plug hole and water ports could be Drilled out to size and tapped and the holes reamed out to size. Then the surface could be faced with a mill.
I have been using a vacuum casting setup to do castings from 3d prints. Most of them have turned out pretty well. I still kind of worry about trying to keep everything together from just the water ports.
Squish band Design
E50 Watercooled Head Drawn in 123d Design