The Newport Bulkhead Mount Diesel Heater is small enough to work in a C Dory 22 or 25. But they are a single point source of heat like the Wallas;
We had the Alaskan heater on one of our cruising sailboats--I put a draft fan and then a circulating fan in, but basically it would heat the lower saloon and to some degree the pilot house. Staterooms, not enough flow to get beyond a relatively small area.
The forced air or hydronic heaters are really better in the long run, just not as romantic...