I think the performer will be an improvement across the board. The SP2P was small runners to max out runner flow velocity at the expense of volume. The performer would probably be an improvement at anything over 3000rpm. Throw it on and see how you like it. The 70's 440 with smogger pistons were never any real powerhouse in stock form. Been there, done that. With a thermoquad and a set of headers it will be a nice running engine, good throttle response and decent mpg.