Very common for stock GM push rods to bend in these motors when they have been sitting around a bit (stuck/rusted valve stem is a usual and common suspect). Interestingly, the stock GM push rods bend easily and are not as strong as the after market tube push rods. Lifters not sitting right, any chance those are on the cylinders with broken rocker arms and bent push rods? if so, probably because no spring pressure to seat it back down after the cam goes to max lift so I would not write them off they are likely just fine.
As an alternative to pulling and doing a full rebuild you might consider getting yourself a new set of trw or sealed power push rods. Dig up another set of rockers (make sure they are not the 59-62 version. Look inside the rocker arm, the oil groove should directly intersect the dribble hole on the rocker. If offset and does not directly intersect,59-62.) You can send them to Rocker Arms Unlimited in California and they can rebuild them good as new. Have the head gone through. You will have to do this anyway if you do a rebuild. Put the motor together and see what you have. You might be pleasantly surprised.
