That's why I mentioned taking an old pushrod to the store with you. If you can't depress the plunger, it's a solid lifter. Now, some may argue that the lifter could be a hydraulic that is full of oil and I suppose that is possible, but all the hydraulic lifters I've bought and installed over the years have not had a lick of oil in them from the factory. It is possible also that someone bought them, pumped them up and then returned them.

Bottom line: find 16 lifters that you can depress and that measure the same from the bottom of the lifter to the plunger surface. Take pad and paper with you if you have to. Measure the total length of the lifter, then measure the distance from the top of the lifter body to the plunger and subtract that figure from the total length. Again, find 16 that measure the same and that you can depress the plunger with your pushrod. If these guys don't have any more lifters, go to another AutoZone or have them order some more lifters in for you to check. Or use another supplier like NAPA or whatever.