Make sure your not hearing a slight exhaust leak, ive more than a few of those misdiagnosed as lifter problems, go up and down each valve cover ( over each rocker arm) with a brook stick held to your ear while the engine is running/tapping, and you SHOULD be able to pin down which is the culprit.
when you have found teh offender, pull the valve cover off and see if the rocker arm to pushrod mate up is good, then check the nut to make sire its torqued properly
if thats no help and it isnt an exhaust leak then its time to try some voodoo to free up teh sticky lifter, MAYBE you can get it to work again withgout having to replace them
OzarkJeep
"Bare foot girls, dancing in the moon light..."