Vintage temp sending units

[Lynn]

Three senders pictured.
1. AC 275 M. Pin connector with correct terminal end. I believe this is correct for 69 Camaro with idiot light. I also have been told it comes on at 275 degrees f.
2. AC 82B. Spade terminal. No idea. Guessing a sender for a light, but don’t know.
3. AC 12V (which I assume means 12 volt). I removed this from a 72 Chevy truck, C50 with a temperature gauge, so would ASSUME it is a sender for a gauge. Truck is inop, so I don’t know if it was also equipped with a light, but the other head had a pipe plug where the sender would go.

Three questions:
1. Am I correct on number 1?
2. I have also read that all the gauge senders used a threaded post connector. Anyone shed any light on this?
3. And can anyone confirm what numbers 2 and 3 are for and the significance of the numbers?
Thanks in advance.

[m22mike]

Correct on #1, not 100% sure on 2, sounds familiar

Mike

[Lynn]

Thanks Mike. I THINK #2 is for a gauge. Came off a 72 C50 with a gauge, and there is one for sale on ebay that says it is for a gauge.

I BELIVE #3 is for a light, but am confused by the 82B.

[Salvatore]

#2 is for console temp gauge?

[m22mike]

Let me be clear on what I posted. The picture of 2 l have no clue on it's apllication . I was agreing with what Lynn said in his question 2 referring to the threaded post.

Mike

[Lynn]

Exactly. That is what I am trying to figure out.

[wrench]

I guess you meant 257 on #1

[Lynn]

Doh!!

Yes, 257.

[HawkX66]

I have #2 on my 69 Camaro big block motor. It's for my console water temp gauge.