Diego,
I think you've dead on about the years, but I think there's a little more to the interchange.
Like you said, the 89 - 94 dsms will all bolt right up, and will plug right in.
However, I believe there's different ratings for the various models, and to the best of my knowledge;
1g dsm's equipped with manual transmissions came stock with 65 amp units.
1g dsm's equipped with automatic transmissions came stock with 75 amp units.
I'm not completely sure about the factory Galant fitment, but all the ones I've ever grabbed off an 89 - 93 Galant at a yard have been the 90 amp units. I like to grab the ones off non turbo cars, as they haven't been baked/abused by the heat of the turbo and exhaust.
That said, the actual rated output isn;t near as important as the unit's actual condition.
If you have deleted the a/c, a 75 amp alternator will do just fine.
I'd rather have a low mile healthy 75 amp unit than a hi mile 90 amp unit that has been "cooled" with power steering fluid for the last hundred thousand miles. /ubbthreads/images/graemlins/wink.gif
edit
Nice looking out on the link! /ubbthreads/images/graemlins/smile.gif