When my front head gasket was shot, it was shooting bubbles in the overflow tank/radiator neck. Would bubble all the time, would overheat until the thermostat magically opened, then it would be okay while driving. Before changing my gasket all I did was drill the thermostat, stick it back on and always check coolant and oil. It burned it in the cyl 3 and 5, never mixed in oil. Would misfire idling too.
That was on a 3.8 though, but those were the symptoms I had on it.