Chad, do an advanced search, lifter preload and xr7 dave. Here's on of his posts. setting lifter preload And get yourself some of the shimms they are in .030" and .060" should be able to get em at any speed shop. They are rectangle with a hole in the middle that you put under the rocker stud.
There is no clearance between anything unless you have solid lifters. You want to shim the rockers with the valves closed. The pushrod will be collapsing the lifter about .060" when the valve is closed.
For all of the non-paying members out there. If you are installing a cam in your car, Dave just posted in the member section at least $15 worth of information that greatly simplies lifter preload procedures.