Wrong Fuel pump

So I was ready to start my 1940 hd213 engine last night and couldn't get the fuel to the carb...after installing and removing the pump about five times I have come to the conclusion that whoever had been trying to get the truck running before me must have installed the wrong pump. The lever arm that contacts the cam shaft installs under the shaft. It appears from the wear on the arm that the pump is in contact with the cam but it's just to giving the pump the full stroke. I rebuilt the pump and it squirts fuel if I manually pump it. From what I read in the book it is supposed to ride on top of the shaft. I would love any input on this and if some knows where I can find the correct pump.