Somewhere on the alternator housing there should be a Delco part number. It will have 7 digits, normally. Any good parts store should be able to ccross-reference the factory number and come up with a year of manufacture and an amp rating. I can't imagine why they would need to know amperage, as almost all the external-regulator Delco alternators used the same regulator, IIRC.
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!