Alternator question

[grubsster]

Hi all,

I guess my question is similar to cwcarpenter98

My question is, I have an 8103-7 alternator which is rated at 105 amps. When my truck is in drive my engine rpm drops to about 550. At this rpm (when my Taurus fan kicks on) my amp needle is jumping like crazy and truck runs poorly unless I give it a little throttle. If I increase my engine idle RPM then my truck wants to lurch into gear. Probably need to change my torque converter again but it seems to drive great the way it is. Back to what I really hope someone can answer is, what alternator can I use at this rpm. I am running the stock crank pulley which I am not sure of the size? Is there an alternator out there that I can swap with or a pulley that will speed up the alternator I am currently running. I will also be adding a vintage air unit this fall.

Thanks in advance.