I have read good stuff about these:

http://www.qualitypowerauto.com/catalog.php?category=4

and these:

http://www.tuffstuffperformance.com/index.cfm/page/ptype=results/category_id=175/mode=cat/cat175.htm

But you can also find a stock replacement from 80s alternators ( 78 amps ) on the cheap and available at many parts shops

http://www.moparmusclemagazine.com/techa...and_alternator/

Consider wiring upgrades

parallel wiring on stcok gauge system