No. Pontiacs don't "come" with shims. Big block Chevys DO, at least under the intake springs (.015" thick, hardened), as the exhaust have the "rotator" under them (on most, but not all). Small blocks, like Pontiacs, did not come from Chevy with them.
Shims are used to restore the installed height when the seats and valves have been ground, moving the valve "up" toward the rocker arm. It is also common among certain builders to "stack" shims under springs to achieve exactly "equal" spring pressure from one valve to the next. Whether or not that particular effort is necessary is debatable.
