The fuel supply system appears to have been redesigned at some point and this part was removed. I don't know what it was replaced with, I am assuming this is the tank side of the tandem pump. You will probably need to re-do that part of the system.
You're going to have to get creative on this. I assume it's an AMF?
A mobile mechanic connected the existing pipes with the valve removed,with flexible fuel pipe. iam not certain how he did it,if you look at the diagrams you can follow the flow. It works, maybe some one else has joined the pipes with the detail. (photos) .
Have the same problem with leaking diesel through this valve.
Can you confirm that it is OK to connect right pipes with flexible fuel hose and for example with plastic tubes and hose clamps? Or changing existing fuel lines with flexible fuel hoses avoiding this valve? Whether there will be any negative sides of doing this?