I had the same problem on a the 300SD. No crow's foot and, possibly no space even if I did have one. The solution was to remove the rubber hose that is just to the right of the pump. It is held on with a small hose clamp. Beneath the hose is a hose nipple that is threaded into the housing of the pump. You can simply unthread this nipple with a socket. With the nipple out of the way, there is plenty of space to get a standard open end wrench on the wrench flats of the primer pump.
Brian Carlton
1984 300SD