NC might have a slight edge on the SF in terms of power. Its negligible more than likely. The reason is as the engines evolved the piston may have changed and the result is the lighter weight piston was more powerful, or the a couple times in the progression the carb throat was increased to bring in more air. Again a little more Power.

I would say a 50flight old NC and a 50 flight old SF would most likely be with in about 100-200rpm on the same prop and fuel same muffler system on the same day.

Troy