Need help with automatic Choke

[1970Chevrolet]

Hey guys, I just bought a 1970 C10 that I plan to fix up and I'm having some engine trouble. When I bought it, it would start but die instantly. So I replaced the fuel pump and lines and got it running. But it doesn't run great. It was missing a few vacuum lines which I took care of and that helped some, but I'm having some choke issues. It appears this isn't the original carb. I believe it's the original engine (305), but I think the carb came off of a 1975ish truck. Anyways, I'm not too familiar with this style of choke, can anyone explain to me what looks like part of the automatic choke system? It has what looks like a vacuum fitting on the front of it. On my truck it's not hooked up to anything. What does it do, and what does it need to be hooked up to? Below is a picture of the carb I am running and I circled the part I'm talking about. Note: this is a picture I found on the internet of the same carb that I have.

[1970Chevrolet]

I just realized I posted this in the builds section. I apologize, can we please get this moved to the 67-72 message board?