Bristols were always better than average quality boats and the 34 is a Herrshoff design that is keel/centerboard which is nice for the VI's as you can get into very shoal spots with the boat. This is nearly a 40 year old boat so a lot will depend on the maintenance and condition rather than what the boat was like when new. Get a good survey of both the boat and the diesel.
Here's lots more info on the boat:
Bristol 34