Howard, I was always taught to check first the bottom face of the lifter. If it bows outward, this means the lifter will rotate as the engine runs. This is good as it exposes a newly oiled patch of metal. If it bows inward, you need to replace it (or them). If you turn one lifter upside down and set another on top of it, the one on top should rock around a bit. This assumes the lifters are not worn to the point of leaking down. Without removing the cam you probably can't tell much, but if it is still running well, I'd be inclined to leave it alone.
