I doubt the oil sender is defective or reading inaccurately, if it was the light would probably not come on most of the time when you take a sharp turn, or in the streets <40 which happens as you constantly brake and accelerate and the oil moves back and forth in the pan uncovering the pickup. The light would be coming on intermittently with no rhyme or reason. I would be willing to bet the pickup is too far away from the pan, and when you take a hard turn freeway entrance, or brake or accelerate too fast, the movement of the oil in the pan uncovers the pickup. If I were to take a guess, the PO lifted the car using the oil pan, bending both the pan and the pickup tube. When the new engine was installed they used the old pickup tube and pan. I am willing to bet anything you want that, even though the pan is still bent, they probably tried to straighten it out as best they could before they installed it, but they never tried to straighten out the pickup tube, as when they looked at it probably looked fine, you probably could not tell the pickup was bent if you just looked at it. So, they assembled the engine with the straightened out pan (which still is probably bent a bit) and the completely bent pickup tube.
