We're Tavana owners as well, in the process of refurbishing.
A little background... Tavana's were sold as "affordable, race-worthy, family boats." in order to make them affordable, you could buy them in various stages of completeness - from bare hull to fully appointed. so, you'll want to look for signs of skill in terms of how it was finished. It may be trashed now, but does the interior look like it was installed skillfully at one time? Electric? sail hardware?
The Tavana's are ridiculously solid boats. Thick hulls. The drop keel makes them fun for near-shore sailing, while also solid if you are off shore. This is a hull that was made to play in the Keys one day and circumnavigate the next. And yes! --Tavana owners have taken their boats around the world.
You can read the original Tavana sales documents on our website: Us Too. » Blog Archive » Four Page Tavana Brochure
and a hull diagram is attached to this post.
If you max out the prop size, the optimum engine HP is ~20. We put in a brand new yanmar 3GM20 and are very happy with it. Steve Lien, also on this thread, did all the homework on engine prop size vs HP and is definitely the guy to talk to. you can see his boat here: Good Old Boat - DockWalk: Glander Tavana
Our hull # is on the bulkhead. I don't know if there is much standardization among the placement of hull #'s.