Oil Pressure Sender
After installing the temp sending in the oil drain plate, it always read low. My engine could be almost smoking hot, and the gauge still read 140 degrees F. So, I installed a T like the one on the left in the oil line coming out of my oil pump. This read a correct temp: about 200 when the engine was warm.
Note one important lesson: the photo on the left shows smooth connectors. These were really, really bad. They are not "hose barbs". I tried them because they have a larger internal diameter, however, my oil line blew off. Yep, it spewed 2 quarts of oil in a couple of seconds, and my oil pressure when to zero. Lesson learned. I replaced the smooth ends with real hose barbs. It worked, but threaded, high pressure fittings would be a better idea.