If I read my plans correctly, the F604 is the bulkhead that the wing spars bolt through. That bulkhead is match drilled to the spars. Hopefully you have a kit where the spars and bulkhead and splice bars match. Way easy for these things to come from multiple sources and actually not be matched. The spars should have an engraved number on them. I think the bulkhead will be engraved with the same number. All should match
So the upshot is - putting in a new bulkhead means you need to match the spar holes. NOT EASY AT ALL. If the spars are not too old then Phogiston (sp?) match drilled them on a jig and can likely make up a new F604 for you. If older... the parts are not interchangable.
From my records, Phlogiston is at 503-985-3212
MAYBE the bulkhead can be reversed, but I doubt the rivet holes will line up. Proper fix is probably new fuselage skins in that area.
If that's not possible, then the wing spars and a blank bulkhead have to be jigged up out of the plane and match drilled. I guess if you have the correct splice bars it won't be impossible.
Good luck!
EDIT:
It is critical that the spar bolt holes be perfectly true and properly sized.