whats the oil pressure look like. i would think stp would have helped stop the tick. maybe get a recording of it and post. clank would be a bad noise. i have seen lifters ticking for a very long time before engine fails, now a clank would or could be a rod bearing going south. stp should have helped that too though. wondering if its something else.

 

Oil pressure is about 1/4 up the gauge from zero when started cold then drops to almost zero at idol when warm. While driving goes up when accelerating then zero or just above when I let it off. Not sure if that is normal.

 

You can not trust the factory gage, they were not accurate when they were new and age does not make them better. . You need to use a hand held gage.

In most "oil pressure" problems I have seen ended up as gage issues.