The face could be warped, its not all that common but is certainly a possibility. A reasonably well equipped machine shop should be able to face the manifold assembly. Don't take it apart, have the manifolds faced as a unit if you decide to do this. Otherwise, get a Rimflex gasket as above recommended. The Rimflex works really well. Tight spot on the inner bolts, yes. Some wrenches just wont fit. I have an extra long Mac wrench, and a smaller wrench that I modified, to fit and snug down the clamp bolts.
