I'm not much of a car person, so the resources I know of to reach out to are... low.

There's 2 Datsun 240Zs in my garage and, while neither run, one is a bit closer than the other. Figured I'd use one as an example for the other, in case I took something apart and didn't remember how to put it back together. Though, one has a part that I'm having trouble naming and it's not there on every image I've seen for the car online.

That is the dealer-installed aftermarket A/C compressor.

My '72 had the same type, it's a York a/c. You have to pull just about all of that off to replace the fuel pump. The smaller round thing above your circle is the fuel pump.

The York compressor is very heavy and as @siteunseen mentioned, the compressor mounting bracket makes it very difficult to change the fuel pump. I had the same set-up installed on my '71 a few months after buying it. But, year later, removed it all and replaced with a modern rotary compressor and mount. I still have my York installation instructions and compressor mounting bracket on a shelf.