I have two thoughts on this subject.
First, give the shop his due for doing what probably amounted to hours of research, and just purchase the alternator from him.
Don't be a cheepskate!
That said, the 2002's problem ISN'T the alternator, the amperage is sufficient to run the car, auxillary lights, stereo etc. Okay, if you have 4 Super Oscars with 100 watt bulbs, it might not. But I digress....
It's your 50 year old, nasty, corroded, high restance wiring harness.
Higher amperage into that system is not going to push the electrons any better than its capacity to receive them.