Just got back my 90 amp Bosch alternator from the local rebuilder - they
included a very nice adjustable regulator; snap off a cap, & set with a tiny
screwdriver while you have the engine running & a (preferably digital)
voltmeter hooked up - piece of cake.  They said they'd sell the unit
outright for do-it-yerselfers.

                                ~ $25 or so;
                                made by 'Transpo' (sp ?) out of Texas
                                order from Nishelle at  Pacific Auto Electric,
                                408/734-1482  (Sunnyvale, CA)
Austin