Anybody running a 100amp alt on their race car?

When you say "stock one wire" that doesn't make sense. Do you mean a factory type so called "round back" with one field wire?

(A "one wire" is one with a built in regulator which has one total wire----the battery charging wire)

I don't know about aftermarket, but the older roundbacks do not put out so good at low / medium RPM. The factory "square back" are an improvement. Also, ultimate amps does not always tell the story. If you look at engineering curves for alternators----and they do exist, at least for Delco---- some LESSER rated output alternators put out MORE at lower / med RPM than some of the larger ones.

And as always---do some checks. Make sure your wiring is up to snuff. If you are running a trunk battery with a separate charging wire, no8 may not be large enough. Sure, it will charge, but it might not see full output.