For those pushing the limits and want an extra piece of mind for their application here is what I did to upgrade my stock harmonic balancer.

First sourced a 95 3.8 mustang harmonic balancer pulley. 94 will also work as well, I'm not sure about other years on the overall pulley diameter but the 94-95 years are the same for the 04 mustang model. I did this because I will be running a supercharger and dont want to under drive the supercharger pulley. Max boost.

As to where I sourced the...

Upgraded harmonic balancer