exhaust, head work, intake, cam, windage tray, blower(turbo or super charge), different carb, electric water pump, electric fan, ......could go on for a while. The things you want to do are increase the ability for the engine to breath and reduce the drag on the engine coused by the accessories. you could just add gears to the rear to make it feel like you have more power.
If you don't go with a blower then add high compression pistons. The higher the compression the bigger the bang. You must keep increasing octane as you increase compression. So you can probably get away with 10.5:1 or 11:1 with pump premium (depending on cam) past that you need to add octane booster, seems i also remember people using water injectors as a cheap way to increase octane.
Fuel injection may get you more power than a carb. Electronic ignition if your still running points. If your running an automatic get a stall torque converter so that the power slamms into the transmission when the engine is into its power curve.