if your planning on running lots of electrical accessories, a welder, stereo,sound systems, mister fusion/hover conversion
etc. [and you still are running the 4G15 motor] you can swap in the 130 amp Mitsubishi unit, Its not a really hard swap, but you need to add a voltage regulator from an old school 80's dodge d150 pickup, and it's wire pigtail [both commonly available at most parts stores on the shelve] also a slightly longer drive belt was needed. i'm running this setup on my Mirage with great results so far idle is about 15 1/2 volts and it never dips below 14 volts, even with all accessories on, If you want all the specs and part numbers or help getting it all setup let me know, I kept all the documentation on the swap and if you guys want me to do a "how to post" let me know.
I can't remember what car the 130 amp mitsu alternator came from, but I pulled 2 of them, so I'll post that info if I can find anything from the numbers on the unit.
Also if you run a galant vr4 or dsm alternator unit [on a 4G15 motor] you need to add spacers on the lower leg of the alternator since it is wider then the 4G15 alternator.