273 power? HOW?
I think that there's no reason to re-build a 273 other than to keep a particular car stock. I know they run very well but if you go to the trouble to rebuild something get the most you can get.
A larger engine means more torque at lower speeds and this is what you'll really feel. You'll notice a huge difference if you get a mild 360 to replace a 273 especially if it's a 2 barrel.