What fitting is this?

Well geez, if it has a brass flare inside you should be able to screw a double flared line into it as long as the flare nut is the right size. We can't see what you have unless you show us.

I'm not sure what you're asking? As in the car itself? It's a 72 dart swinger.

The MC is a 15/16" 4 hole deal originally intended for front disc, rear drum applications. I'm using it to switch to manual brakes because the engine doesn't pull enough vacuum for power brakes. My car has a disc conversion on the front and rear, and I removed the residual valve from the rear circuit on the new MC. I'm not sure what all cars had this style of MC but I'm guessing it was a lot of them. Besides that info I don't know what else to supply is there anything else I'm missing?