high amp altenator

I want to put a high amp altanator into my 93 xj 4.0. The stock one is rated at 90 amps. I have seen some discussion that a newer model year altenator is rated at 125 amps is that so, and will it fit? Also has anyone taken a junkyard altanator out of somting that can be modifyed for the 4.0 that has about 120-150 amps. I know there are mean greens out there but I dont whant to spend the 300 for one.