A radial diesel aircraft engine, probably the same design, used to be on display at the Henry Ford Museum in Dearborn, Michigan. I think they may have moved it into storage when they reorganized their aircraft exhibits, though.
As fuel prices get higher, there's been a resurgence in interest in diesel aircraft engines in the last few years. This is especially true in Europe, for obvious reasons. There are now a few options for diesels in light aircraft, some purpose-built and some conversions of automotive engines. I believe there's one company making one based on a VW TDI, and another making one based on a Mercedes common-rail engine. (In spite of the old joke that water-cooling an aircraft engine makes about as much sense as air-cooling one in a submarine, there are some distinct advantages to water cooling, especially for diesels.)
