There was once an aftermarket stator assembly for the external-regulator alternator that dramatically increased the amperage output, up to 100 amps, IIRC. It's actually 3 separate sets of windings on the same size stator frame as original. I used to install them 20-something years ago. If there's a rebuilding shop in your area with an old geezer who has been around the business awhile, he will probably know if those stators are still available.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!