The only issue I am aware of Ron (informed of by a 250 2C racer) is the frame sometimes cracking near the bottom right engine mount but only heard of on race bikes. Apparently some race bikes have this area reinforced by welding some webbing.
Parts appear no less rare than current Benelli parts. German ebay usually has lots of parts available, as does www.benelliparts.de.
I have one sat in my garage which I hope to turn into a racer but that's on the back burner right now. So you never know; I might have some parts going spare myself.
Lovely little bikes though. Not overly powerful compared to other bikes of the era but they do have a reputation for handling well.