Diagnosing Gen 1 Mount Failures

With the great help here so far, I’m 99% sure I have an issue with one or more of the mounts in my 13 Volt.

It SOUNDS like it’s coming from the driver side when it happens, but it only happens when the ICE is running. Could it still be a trans mount? Or does the fact that it’s silent on electric rule it out?

Is there a way to diagnose which mount it might be? Should I really just do them all anyway?

Thanks!