Oil pressure switch/sensor?

[Harmon]

1986 Chevrolet C10

Was a 305, but converted to 350 at some point.

There is two sensor/switches at back of block near distributor.  I know they deal with Oil Pressure, but do I need 2?
One looks like a round fuel filter and the other looks smaller and narrow.  They are both attached to that brass fitting.

[bd]

Both are needed.  The larger of the two is the sender for the oil pressure gauge.  The smaller may switch the electric choke.  Post a pic.

[Harmon]

I attempted to post pic, but the size was to large.   Ok I understand the purpose of them both now...thank you.

They of course were both unplugged.  Is there a way to test them to see if they work?

[bd]

Resize the pics in MS Paint or similar software.

The gauge sender is a single terminal analog device and the choke OPS is a dual terminal digital device.  Both can be checked with an ohmmeter. 

With the ohmmeter connected between the gauge sender body and single terminal, the meter should measure zero ohms with the engine off (zero PSI), climbing to as many as 60 ohms at maximum gauge scale, which typically is 60 PSI.  The oil gauge calibration is linear, so the sender resistance at 30 PSI for a 60-PSI gauge should measure 30 ohms, etc.

The choke OPS contacts are either open (<5 PSI oil pressure) or closed (>5 PSI oil pressure).  With the ohmmeter connected between the two terminals of the OPS, the meter should measure infinite or "OL" with the engine off and zero ohms with the engine running.  Both terminals should measure 'OL' with the ohmmeter connected between the individual terminals and the metal body of the switch, regardless of whether the engine is running or off.

[Harmon]

Ok I have got conflicting information.  Can this be cleared up without photo?

I have 86 Chevy with 350 that used to be 305. 

1. I have the big fat round Oil Sensor with one connector to be plugged in.
2. I have the smaller typical looking Oil Sensor with two connectors on it.

I am replacing the electric carberator with a non electric one, elimnating the electric choke.  Which sensor can I get rid of in that case?

[bd]

#2 (Choke OPS)

[Harmon]

Great! because I bought the bigger fatter sensor/switch already. 

While were on that carb.  The wire that runs to the carb and plugs in to front right of the carb, it has a short wire off of it that looks to plug in somwhere, but it never was hooked up when I got the truck, what might it go to?