Hi Keith,
Yeh, a 350 would be a good bike for the Motogiro. (Personally, I like the earlier bikes at least as much as the later ones ... maybe even more.)
I never advise people on price - after all, only you know the relationship between the depth of your wallet vs. your aching desire to possess

... The main thing, IMHO, is to be confident about condition, by which I really mean, is it genuine? Buying a bike that some monkey has 'restored' with non-original, ill-fitting parts, or with significant parts missing, can lead to a lot of grief and expense. Go prepared, ideally with someone who knows the bikes (Tony Brancato offers an inspection service in the UK, btw- also, do join the DOCGB if you're not already a member); but, as a minimum, assemble as many photographic references as you can find. And don't be scared to ask to have covers taken off to see what's underneath - a genuine seller may be surprised, but shouldn't be offended.
(A guy we met on the Giro this year had a lovely 350 Mark 3, a blue one. He hadn't owned it long. Anyway, his clutch failed while he was out riding with us. We took the cover off on the side of the road to discover an absolute dog's dinner of clutch actuation rods. With a bit of fiddling, we got him going again, but his confidence was understandably pretty shot and he decided to sit the rest of the event out. Not what you want ...)
Buona fortuna in Italia, ma caveat emptor!
Ciao
Craig