Where does this wire go? Found under oil filter.

So M&H didn't include the insulator for this terminal. That doesn't mean the factory didn't put on on it. I dont know the consequence of this terminal touching ground where there is only a warning lamp. Maybe just lamp stays on? I know shorted to ground can kill a oil gauge. There isn't a similar bare wire terminal anywhere else. There is my sign.

yes the light just stays on. The early ones only had lights I believe so they could save a few pennies by not having the cover. The original harness on the 63 did not have a cover either.