OOOoooooohhhhhhh..
i could not figure out where that came from today. I upgraded to the Chevy blower motor and cage. Awesome and easy. Of course that led to flush & fill, upper and lower radiator hose change, new heater core, new thermostat, cleaning and painting the thermostat housing, etc etc.
and at the end of the day there was a little clip on the floor - now I know.