Hi Clifton,
Your Z cars seem really interesting! Ironically enough, I occasionally check out Zs in case one is irresistible!
I have to say, you are ambitious with your plans! I would advise you to get in touch with Richard Winter at Banks Service Station (aka Europa Engineering
http://www.banks-europa.co.uk/index.php). He's probably put one of every motor into a Europa! If he hasn't installed the Toyota motor, he might have some tips for you. I know he's installed a V6 Alfa Romeo motor in a Europa. He also has some interesting upgrades you may be interested in. When I was calling him, the best time was during his lunch break (12 - 1:00 GMT).
That sort of power will require some body upgrades. If you're interested in keeping the Lotus flavor, Richard probably also has some fender treatments - I know he sells reproductionType 47 and Type 62 body shells.
If you search the Knowledge Base of the lotuseuopa yahoo group, I'll find that the VAST majority of engine swaps are for other four bangers. I have heard of some bigger engines talked about but never any that had been finished. Of course, don't be afraid to ask questions from us here, too. Who knows, we might have some answers!
Good luck! I can't wait to see pictures of your progress!