alternator tech help

Lets assume yours is a square back and rated at 60 amps. That rating is equal to the sum of its parts. Bypass the regulater and full field the altenater, then go to a high rpm and you might see 90 + amps come out of that altenater. If the wiring is sufficient to carry that much current the altenater will overheat and die.
Altenater A is rated at 60 amp/hr at 2000 rpm and 205 degrees.
Altenater B is rated at 120 amp/hr at 2000 rpm and 205 degrees.
Altenater A would be working its butt off all the time and insufficient at idle.