Only use an impact tool if you aren't reusing any parts of the alternator, otherwise do it by hand to prevent damage.
Glider made a very good point in Post #11, in fact there is a "side note" in the service manual NOT to use an impact driver...tey just don't state why...as the vibration/shock can unseat the "opposite" design magnets in the alternator or break the fasteners loose, possibly causing latent (hidden) damage if either the stator or rotor assemblies are reused. Why do you think they weld rather than use removable fasteners in there?
I would not impact it also. If it was locktighted when it was installed, hit it with a heat gun first.
Hundreds of ft/lbs should not be necessary.
CatWoman I have never seen where a breaker bar with a 2' pipe and a strong arm won't get it off.:s
I had a similar problem with the 94 Dyna thought id never get the compensator nut off i had a 4 foot pipe on the end of the breaker bar wouldn't move and eventually used an air impact wrench and a lot of heat to get it to move but did pull all the alternator parts out to see if OK been across Europe twice since then without fault
Brian