Steve,
I have an older Mozzie with timber hulls and timber foils and while it is best to go for the low maintenance option the timber hulls can still be competitive. If you do choose to go the timber option look out for cracks below the inboard side of the front beam. If this is found it's not too hard to fix with epoxy sealer, fibreglass cloth and epoxy filler.

It is also important to go for hulls that are as light as possible (foam frames and minimal use of internal stringers)so that you can keep up with the other minimum weight Mozzies and have as much buoyancy as possible. This is where the newest Mozzies have even greater advantage with maximum buoyancy already designed into the mould.

If you go for timber I would also recommend that you go for hulls that were built by a professional boatbuilder rather than a backyard builder. They usually had the right strength to weight ratio but were probably raced and stressed allot more. What a dilema !!

As you say it's easy to buy a new sail and rig to get best possible forward thrust. I'll let you know what difference a new powerplant makes in a couple weeks when I get my new sail.

Good luck with your search.