+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.
Carl