I have a 64 Galaxie with a 390. When I drive the car for more than 10 minutes (enough to warm up completely) the oil light comes on. It doesn't just light up, though, it slowly flickers, very dimmly when I come to a stop sign (i.e. when I put a greater load on the engine. It's an automatic). Eventually it stays on bright. When the engine cools this starts all over. The engine runs good and strong with no temp issues even when the light comes on. the temp gauge shows right in the middle.

Initially, I thought the oil pump didn't like the thinned (hot) oil. But this engine has all factory parts and I changed the oil pump with a new-original replacement. I still get exactly the same issue with no variation. If it were the pump, it's not likely I would get the same symptoms on two different pumps. I'm going to try to change the oil sending unit today, but my question is this:

To my knowledge, only the pump and switch affect this oil light. Is there anything else that might cause the light to come on like this? In case it matters, I had the timing set on the car recently after I rebuilt the heads and it runs like a champ, but I never had this issue before.