Oil Sending unit location on 250 inline 6

[Dcdoc45]

I apologize for this post if it is covered somewhere else, I did search I promise.
1977 Chevy C10 Custom Deluxe w/250 I6 motor w/combined head.
I want to replace the idiot light with an oil pressure gauge. I can't for the life of me figure out where the sending unit is on the engine block! I see some vacuum switch type sensors on the block but nothing else.
Can anyone try to describe or better yet have a picture of the location of the sending unit so I can replace it with the sender for the aftermarket gauge?
Thanks

 

[RetroC10Sport]

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Number 33. Shows it to be on the passenger's side of the block towards the back.

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Just above the starter.

 

[74 Shortbed]

Here it is right under the side cover.

 

[MikeB]

And the several wires running to it tell me it may be like my 82 truck where the electric choke doesn't get voltage until engine has oil pressure. I'd recommend keeping the switch and adding the gauge using a "tee". Otherwise you will have to jumper around the switch for the choke to open.

 

[74 Shortbed]

It's a 78 and it has 3 wires, I'd say one is the choke..

 

[Dcdoc45]

Thanks for the replies!!
I'll get that done this weekend.
Would a simple brass tee pipe fitting work to tee it off of?

 

[74 Shortbed]

Yes, that is typical..