Oil Pressure Gauge Sending Unit

The oil pressure gauge in my 77 3.0 is not functioning correctly, so I purchased a new sending unit. As I was looking at the existing sending unit and found the existing unit resembled the oil temperature gauge sender and not the new unit purchased. I checked the part number on the new unit, and found it to be correct. On the front of the engine another sender is mounted and according to everything I have read, this is the oil temperature sending unit. What has me confused is that another sender unit is mounted on the front of the engine above the temp. sender. This unit resembles the new sender I purchased.

The questions are, what is this sending units function, is it possible to relocate the oil pressure gauge sending unit to this location and still function correctly, or has a previous owner swapped the two units accidentally?

Thanks in advance for any info regarding this one.

Sorry folks.
I didn't mean to sound incompetent.
I was going by the Hynes manual which indicated that this pressure gauge sender was located on the back of the engine. They even have a photograph of said sender being mounted next to the oil thermostat. I have since found the correct information without the help of the Hynes manual.