Oil pressure senders

[VAL]

So, I replaced my oil pressure sender a couple weeks ago on my 86 k10, 350ci. My gauge is still acting erratically. I figured it was a wiring issue. I pulled my transfer case today to reseal it, and I'm looking up at the transmission tunnel from underneath the truck and saw what I thought was another sender, opposite side from the one I replaced. The one I replaced was first picture, the one I saw from underneath, was the second picture. Now I'm confused. Is this normal to have 2 oil pressure senders?

 

[Turbo4whl]

The left picture is a pressure switch for the electric choke (2 terminals). The larger one, on the right, is the pressure sender for the gauge (one terminal).

 

[VAL]

Thank you Turbo4whl. Just when I thought I was fairly familiar with these trucks, I get schooled.