I will be starting my rebuild on the '70 this week and wonder what kind of difference in horepower/torque there would be between an identically prepared 306 and 331. I will be using Windsor Jr heads, an Edelbrock F4B intake and headers/X-pipe exhaust either way. Carb and cam will depend on the stroker option but nothing to wild. I am not looking for any exact numbers just some rough estimates. Believe it or not my engine builder thinks that I might be happy enough with just a nice 306! He said it would be plenty of engine to spin the tires and have fun. I'm sure it would be better than the seven cylinders I have now!