Definitely do a cam over rockers. If you've got it that far, there's no reason not to. It seems you're pretty set on keeping it NA...headers and cam are about the only other things to do. Also, finding a thinner head gasket will bump up the compression and more if you mill the heads but you'll likely need new pushrods. You'll just have watch piston to valve clearance if you go with higher lift from a cam/rockers with thinner head gasket/milled head.