Spendy, but seeing if anyone has gone this route, already. Looking at the FJ60 one, specifically.
www.powerbastards.com
120A High Output Alternator for 1979 - 1987 Toyota Land Cruiser L6 4.2L
120A high output alternator for 1979 - 1987 Toyota Land Cruiser L6 4.2L. Built for car audio, upgraded electrical performance, and extreme-duty applications.