Thanks OM. You are correct the old head has the 4H7258 casting number embossed on the top of it. Searching for the head seems to bring up a lot of 8N6000 and 8N6004.
Superweld says these are off D342 non spacer plate as well 8H5980, 8N4229 and 7N6357
7800 pounds. That will test my jib out on my 944😊
Regards
Phil