looking at my action, that action or bolt head may need a little extra work. Becuase the lugs are out back the floating head has a tendency to hit the action just in front of the ejection port. This has some raised burrs on mine so need to cratex off. If yours does too, you may consider having the gunsmith see if he can silver solder or weld some extra material on and machine it back to normal, maybe without the extractor groove, and put a touch of bevel on it. This should help it feed. I am also curious if the barrel will need to have a little clearance cut for whatever extactor you choose?
Please keep us informed about what is recommended. The 788s are wicked accurate little rifles. Mine was my Fathers and I love it. Light, handy, accurate.