<DEEP SIGH>
There are tons of stuff written in the back pages on how to make power, but here it is:
Start with everything in good mechanical condition. If it is worn or missing, replace it.
Read Gordon Jennings book before you start:
http://www.amrca.com/tech/tuners.pdf
Send your head off to an expert to be rechambered.
(Ken and Joe have great reputations here)
Set the squish to about 0.030".
Raise the exhaust port 1mm doing a nice blend. Don't remove too much metal.
Open the lid on the airbox with some holes to the area to that of a 26mm circle. Not much.
Learn about reading plug ("Plug Chop") and jet your carb.
Do this and you will have added about 10 HP or more for about $100.
Stroker cranks, big bore kits, pipes, iridium plugs, boost bottles, water cooled heads and big carbs won't make you this big of a HP increase.