I say if it is really a "Grail" Masi bike = FIX IT!....partial of full resto, preferrably by a professional who knows what he is doing and is aware of the bike's importance. Only reason to keep that dent is if it had some sort of historical significance maybe related to a famous race incident with a famous pro riding it. Otherwise, it's just an ugly, rusty wart on a beautiful bike that needs to be taken out asap!

Chombi