I want to confirm something. The temp sending unit on a 71 351c is at the base of the thermostat???. I noticed on the water pump there is another unit. What is this?

 

There are two. One of the side of the block on the drivers side, and one on the front of the block right about the timing cover. There are two oil pressure sending units as well. One of the top of the block on the rear, and one on the drivers side front of the block near the fuel pump.