My buddy Josh rebuilds starters and alternators... The stuff you get 're-man' from Napa, Carquest, etc... Is put back together by Juan Valdez. And they overcharge.
That 300 is probably Fords most bullet proof motor they made. I can ask Josh what alternator to use if you'd like? I can call him tomorrow.
I had a hard time trying to find one for mine and i couldn't get it rebuilt ( case was junk) so i bought an old style GM alternator (single wire) and had a machine shop make me another pully to fit it. Works great and you can usually pick-up those alternators for about $40.