My '81 was stock rated at 63 amps. Then when it finally died, I took it over to a local guy (very reputable) that does starter and alternator rebuilds. He did a complete overhaul and "beefed" the alternator to 100 amps output max./ 70 amps at idle. It was cheaper than buying one from a auto parts store. And he even warrantied it for life.
So next time you have a alternater "crap out" you might want to check out a local auto electric/machine shop in your area and see if they can do the same for you. (as long as you can lay up the car for a day)
Amazingly in my '81 I had the same problem. When the stock alt failed I check the book for the correct replacement (which they said was an 85 amp unit) Well, guess what? Mine was also a 63 amp. So I dug around and paid the extra $$$ and got a "correct" 85 amp Alt. It is larger and required a little tweeking the slot size on the support arm but now when I turn on every electrical device and the a/c, the alt gauge doesn't even move. Go with the larger capacity unit if at all possible. It's worth it.