Had one like that on my '64 Custom/427. Two senders---one for the oil pressure idiot light, and one for an oil temperature idiot light. Scared me s***less when it came on at the end of my first trip down Milan. The guys from DST were there and I was told it was typical for that momentary 'hot' light after a load such as a trip down the quarter.
I fixed it by creating a deep sump pan from a spare from the boneyard. Cut a hole in the factory pan to let the pick-up stick through---I extended it with a piece of 1/2 inch thinwall---and used as much of the boneyard pan as I could to deepen the pan. The remains of the original sump acted as a sort of baffle.
No more problems with the idiot lights. (I also installed an oil pressure gauge.)
KS