Good post, Dave. As noted in your blog, lifter noise at low rpm is usually caused by gum deposit from the oil. I have had some success cleaning the gum with a can of Rislone. Rislone is a detergent that is added to the oil, preferably with fresh oil. It is not a quick fix, the engine has to ran, at speed, for a few hundred miles.
I will not recommend replacing individual lifters. If the lifters are having issues beyond what can be cured in Dave's blog, all lifters should be replaced. Most likely the camshaft is worn and will need replacement. Putting new lifters on a worn results in new, worn lifters.
