The tag is gone from my alternator and I am wondering how my amps my alternator puts out.

Its a 2000 T600 with a 12.7 Detroit,500hp.

I am guessing 120-140 but hoping someone might know.

It's probably more in the range of 165amps. My '02 Volvo with an ISX has 165.

On the flip-side, my '99 Chevy S10 Blazer has a 135.

Try the maintenance section.

It will depend on the model..............but probably 130 to 165 amps