RE: Engine Factories?
CMB is another Italian manufacturer. They are most known for their marine engines (.21, .45, .67, .84, .90, .100 sizes) but they also have a line of car engines.
CMB also manufactured the MAC line of engines designed by Andy Brown. They were also mainly marine engines (MAC 21, 45, 67, 84) but they had a buggy engine too (of which I own 2). The contract between Andy Brown is over and from what I heard he's looking for another manufacturer.
There are a few Russian manufacturers too. I used to run the Kalistratov 45, also a marine engine.