Stuck lifters (in the bore, not talking about lifters w/internal probs) will bend p-rods in a NY min. if the engine is cranked over before they're loosened.
Check for bent p-rods when you get the v-covers off. Then, with the eng. running, v-covers off, take an oil squirt can and fill it w/Marvel Mystery oil or ATF. Squirt/dribble oil down the p-rod onto the lifters as the engine runs, if there's still tapping coming from any of the lifters after the p-rods are corrected.
This WILL NOT harm the engine in any way, shape or form.