Upgrading my 340

"Take the time to really understand your timing--intital, curve, total, vacuum. Almost everyone drops the ball here."

I know nothing about this. Love to learn more, can you enlighten me as to what to look for and how to even change results? Or point me to a good book to educate myself with this....I believe the air gap was mentioned in a couple previous posts, I will surely look into that. Do different brand carburetors really outperform one another? I've got a 650 double pumper, would there be that much of a difference? My carb is jetted to my engine....is the boost in power substantiated in getting the car returned to the holley?? But the intake is worth looking into and definitely the header pipes as well.