Dave, the colour of the engine is one of the standard clues to its age and type. If you are trying to preserve originality (as distinct from building a machine that pleases you) you should stick with the original engine colour. Incidentally black Briggs engines came later than white ones, so if you paint it black you might offend both breeds of enthusiasts: those who value it for being old, because you're making it non-original, and those who value it for being less old, because of the mutton-dressed-as-lamb implications.
