Jamie, that's a very good question! I would guess this combination would be good for 65-70 horsepower and 155-165 ft-lb torque give or take. Dual carbs, a modern ignition system, and free-flowing exhaust would likely give another 5 hp/10-12 ft-lb. This is probably in line with the average "hot" late-30's to mid-40's 'banger. IMO, valve float is the limiting factor in most of these engines, and the primary reason the OHV conversions and larger displacement V8's could not, for the most part, outperform the 'hopped up' flathead 4's on the lakes. To combat this, I had steel valve spring spacers machined to increase spring pressure, which should reduce float. That said, my A motor will be limited to 3500-4000 RPM, as that's probably the practical limit to stock (styled) con rod fasteners, shimmed valve springs, and splash oiling. This corresponds (roughly) with a 90-95 mph top speed (with stock gearing and 30" diameter tires)....a good speed in the late 1930's - early 40's.