Throw a high-compression head in with the dual carbs and exhaust and you'll have a very noticeable power increase, one that feels much more than the dyno will show. The flat six has little surplus of power in stock form, any increase is dramatic and welcome. And then there's the sound of duals on a six!
I just gave a stock dual manifold to a buddy for his daughter's 53 Plym, but some lowlife swiped her carburetor right off the engine so he's short one. When he gets it going I'll post how it runs.