the stuff you mention won't really do that much. The undersized pulleys will free up a bit of horsepower but...
The 1.5 ratio rockers are pretty much standard to every engine. The air filter might help the engine breath better but you're not going to see any major increase in power. The carb plate is more for keeping the carb away from heat to prevent boilover. The ignition system will give you better spark but again, i don't know if you'll really notice it.
I think you're going to have to get into some real parts if you want more power. If you don't want to get into major engine rip down then start with a bigger carb or some better headers or maybe a better intake. If you want to do more then put in a bigger cam and get better heads.
No offense, but the stuff you suggested will give you minimal changes.