If they're '68-71 heads, the best thing you can do is install a set of Crane Kool Nuts. They have an Allen set screw that'll allow you to adjust your hydraulic lifter preload. This is especially important if you're running an aftermarket cam. If you've been just tightning them down to 22lbs and then go to the Kool nuts with a lifter preload of 1/4-1/2 turn, you'll notice a big difference in idle and performance.