Rob,
For me, three factors will go a long way towards determining which transaxle you'll want: horsepower, driving style and the size of your bank account.
Click
HERE for an excellent place to start your research. There's some real good information in that thread.
Be sure you take up Martin's generous offer. When I started my research into 40s, several long conversations and a close-up inspection of a replica made all the difference.
You're in for a great adventure. Welcome to the forum.
T.