If your budget will swing just buy a cylinder head already done up. If not clean up the ports on your existing I'd go with something mild like the GX cam or close to it. On the flywheel you have a couple of options but for street I would not run anything lighter than 14lbs.
Mild porting, Cam, 32/36 and extractors should get you about 15 hp give or take a few. One thing to remember is that the more you mod an A-series the higher up the rev range the power band goes and the standard gearbox starts to become an issue due to the huge RPM drop between gears. It's best to give up a little so that the drivability doesn't suffer

Tom