In 1960, Harley Davidson bought a 50% stake in Aermacchi Motorcycles. By 1974, Harley Davidson owned 100% of Aermacchi Motorcycles.
Tony Foale did some interesting work with putting four valve heads on Aeramacchi 350cc and leading link forks.
The 350cc seem to be a popular vintage road racing motorcycle alongside bevel-driven single cylinder Ducatis.
Variations of a theme: