Ford 4000 Simms pump help

[JF in MI]

I have a question for any Simms injector pump experts out there. I am getting fuel leakage at the point indicated in the picture. It's not the tube nut on top but is seeping up out of the block on top of the pump. As far as I can tell from any diagrams I have looked at there is an 'O' ring on each of these flanges that seals them on top of the pump. Can these flanges simply be removed (unscrewed or whatever) and the 'O' ring replaced with no issues or will this screw something up in the pump requiring a complete rebuild?

 

[Dieseltech]

It takes a special splined socket to remove those holders. The EARLY pumps used a nylon type seal ring between the delivery valve and holder. the LATE top face sealing delivery valves use an O ring BETWEEN the delivery valve and plunger barrel top. Usually when any leaks start showing up the wise thing to do is have the complete pump gone through, and by that time Simms pumps need the governor weight kit too.