Alternator pulley size to fix dead alternator

[mgt92]

I have a 99 mustang cobra that has been burning up 1 alternator per year for the last 4 years since putting my Vortech Strim on. I have checked all of the grounds/electrical and have not found any issues. I have read a lot of posts on the 03 forums about heat and overspinning killing the alternators. 2 of my alternators were Ford OE and the last two have been NAPA. I know NAPA is junk but they are warrantied for life so I need to try to make this alternator work.

I am trying to figure out what the best size pulley is to get and from where. Some people recommend 3.2 and others bigger.

Thanks,