I would agree with that jckkys, but with caution to others.
I would prefer to keep it too, but all the books and charts say that this is too much current to pass through 10 feet or so of 10ga wiring for more than just a few moments with any safety factor. In some cases they say it's WAY more.
Granted that's probably with a large safety margin and they have to CTA's whenever recommending something, but I take those to heart too when upgrading. Especially when we don't know the overall condition of someone's 40-50 year old wiring.
Otherwise, I'm totally on board with a 100 amp 1G and it's what I use on my full-size (different wiring scheme from the factory though), with the lower output 70 amp model on my stock EB wiring.
Just trying to play it overly safe with the wiring belonging to others here is all.
Full speed ahead and the heck with my own!
I actually plan to use a 130 amp Explorer alternator with my new wiring, and upgrade to 8ga to run through the stock ammeter. Just not sure I would recommend that to others until I've lived with it.
Your 20 year experience with the 100 amp is interesting though. I'd guess you always had wiring and batteries in good shape too? The very first total re-wire I did was because a 120 amp GM upgrade melted the stock charge wiring on a '69. Less than a minute after the first startup in the morning and the entire harness went up in smoke.
Hence my usual caution...
Paul