Jester's method is the "expensive" right way to do it. However, those parts are pricey. For street motors most now use adjustable pushrods, which are plenty strong enough for 99% of the street engines out there. And.... only cost around $150. A set of adjustable rocker shafts will cost you a minimum of $400 and they'll probably need to be rebuilt. Add custom length push rods and roller tipped rockers and you're going to be spending upwards of a grand. Money well spent if your going racing, but for a mild street engine it's probably a little overkill. Just my opinion.
"Instructions are just the manufacturers opinion of how it should be put together". - Tim Allen