The 290/.650 cam was designed to move air in and out of cast iron heads. The Indy heads don't need that much duration, it just makes the engine lazy. Put a smaller cam in there and the engine should perk up. Before you tear it apart check the cranking compression and then recheck it with the new cam. You'll most likely need to change your ignition curve and re-jet the carb too since the smaller cam will make the engine more efficient. Take a note of your manifold vacuum at idle before and after. It should go up by a bunch.