Thanks for your input. That's exactly what I've thought.
-mrberl
I don't know if the 99 alternator is dimensionally identical and attaches in the same manner as a 98 but I will go in the defense of Toyota/Lexus in their choice of alternators. They chose a 120 amp alternator for a reason. Going with an alternator with reduced capacity MAY mean that under really high loads, your demand for excess power comes off of the battery. If that happens, then you get reduced battery life. Those conditions MIGHT happen on the proverbial dark and stormy night when you are running headlights, wipers, fan, a/c, etc.
In the classic car world, some of our cars came with 35-45 amp alternators because we have so few power accessories. As guys and gals mod their cars with aftermarket stereos, a/c and such, the demand on their alternators is too much and they buy alternators with increased output.
If I were in your shoes I would rebuild your existing alternator or buy one of the proper amperage.
Just my thoughts.
Gary