Initial test of starter failed last week. It was ultimately due to the 7 year old Odyssey PC680 battery. Voltage at the battery during that start measured 8.9. New battery installed plus changed to a new starter removed from a new O360 that didn't require it. Prop spun like it wanted to go somewhere. Oil pressure rose to 8 PSI before I stopped the test. Woohoo...
Replacement starter from a new O360 not needed by owner.
Solved my concern about potential grounding issue with battery hold down clamp;
