+1 on Leece-Neville large case alternators. Unlike small case alternators, these will put out their rated power even when hot. Very solid.
I had a Leece-Neville on my last boat and had it rebuilt and some diodes replaced (the alternator
had given heavy service
for six years and the rebuild
was about $100). These guys did the work and I was very happy. I did it all by email/mail.
Toledo Truck Parts
They also sold alternators and seemed quite familiar with marine
applications so I think a call might uncover some great options. These are the kind of guys who seemed like they had bins of mounts hanging around (or if they couldn't find one they could make it in 20 minutes).
Once you get past 110 or so amps you have to go to twin belts. You'll need to think about the pulleys on your engine