Usable power for the street?

Steetable depends on many many factors. There is no number that is all encompassing. My daily driver 3500 dually makes 705hp to the tire. But it weighs 7600 pounds. Completely streetable. My 63 falcon makes just over 600 and weighs 2650 and is terrifying. It’s all relative. For a stockish A body with a small block the fun really starts at about 400hp and a 360 magnum will get there a whole lot easier and be much more steerable than a 273 will. Just my opinion.