Well, entirely opinion, but i say the second option- ie cage and sprint

is the go.
Why? you could easily spend $30k getting it to concourse condition. Will you ever get your money back? Definitely not. It would be a bloody nice car, and hugely appreciated by a lot of people, but i think if you got it to that level you may find yourself staring at it in the garage.
On the other hand, spend maybe $5k, get a cage, tidy it up (nothing special, just reliable with maybe a few small modifications), and spend the rest of your $30k concourse money thrashing the crap out of it round a track

The fun for money ratio is unquestionable.
Is what i reckon anyway