I don´t think the cam is holdig back your ET´s much. Duration is pretty good where it is and the heads won´t flow much more in higher lifts. You could pick up a little with a roller, but for the money invested I think it would be a disappontment.

If you invest the same money for some head and intake work, you will gain a lot more. Those stage 2 ported RPM heads are not much bigger in cross section area than stock RPM heads, and I bet you don´t make power above 5500rpm. Open up those runners and you will see a big gain.

If the Super Victor isn´t ported it will cut the flow quite a bit too. I recently ported one and gained almost 20cfm with fully ported RPM heads.