well it gets tricky with cars and not trucks because cars are more limited to optional alternators. I would assume that you like to park and listen to your music, if so you should look for an amp that puts out alot at idle. If you like to redline the car all the time like most 4 bangers then you need one that can accept the rpm that you would run it. You dont really want to spin the alternator more than 17000 rpm. If you dont gas it all the time then there are more options, you can change the pulley size and and make the alternator spin faster at lower motor rpm. This is another reason why the performance guys change their pulleys, they dont need the low idle amperage but they rev the hell out of the motor so the need to make sure the alternator spins slower. Albeit there are probably alternators available that can handle 17000+ and still provide lots of power but they will likely caost a lot more. As far as what you should look for, 100-130amp alternator should work nicely, I am guessing you stocker puts out 70. Also if you change the wire that goes from the alt to bat to a #6 this will also help transfer power more effeciently. Do you have a cap? What battery, batteries?