WOULD THIS 100 amp alternator work

Sounds like the perfect plan and if you decide to run the 100 it should be all safetied up with all the mods done. There are guides online to build your own dash voltage regulators, I built a few but they were very slow to get the gauges up to proper readings and ran hot. Pretty sure we were using too small of a 5 volt regulator chip and the newer guides tell you to use a much heavier chip and heat-sink it.
Anyways sounds like you have a plan so good luck with it when you get it all done.