I’m rebuilding a 250 that came out of a 1973 Chevy C-10. I need some help identifying what sensors or other items came out of some of the holes on the block. See attached pictures that will correspond to the below.

Locations A and B:
The image can be found here: https://imgur.com/a/luAhBks

A: Oil Pressure Sensor? (I already installed one so I think this is correct)
B: ??

Locations C, D, and E:
The image can be found here: https://imgur.com/JU13WPj

C: Water Temp Sensor??
D: ??
E: ??

Thank you!

B coolant drain
C and D coolant temperature
E exhaust heat for choke pull off

I think... could be wrong.

Hi,
I agree on A, C, and D.
B goes in the oil gallery I think.
(I want to guess choke related.)
The coolant drain is on the other side of block.
E is a connection for a PCV, should be going into intake plenum.

I too, leave room for being wrong.
Early 60's engines have less holes poked in them.

A & B are oil C & D Temp. E is a vacuum port The PCV port is on the 3/4 runner next to the carb. There is and drain plug on the lower driver side of the block.

Larry,
They used both locations for the PCV connection.
I have no idea when or why they used one over the other.
see:
https://www.flickr.com/photos/raleighpro531/51855233418/in/dateposted-public/

I was wrong. Thanks for correction!

Pete I think the reason is Some of the earlier intakes did not have a spot on 3/4 runner for the PVC. And I think in the later years they also used That port for Power Brake vacuum?