The lifters are dirt cheap, replace them. Mine has 240,000+ miles on them and they were concave instead of convex like they're supposed to be. You could clearly see the wear pattern.
Anyway here's the rules:
New lifters on old cam - OK
Old lifters on new cam - NO
If you decide to reuse the lifters for some odd reason make sure you put them back in the exact same order from where they came out. They're a matched set and will cause wear and failure otherwise. Use a quality zinc assembly lube (GM EOS http://www.summitracing.com/parts/nal-88862586
that you can get from your local dealer.) and coat the cam as well as the bottoms of the lifters in it. I use a clean coffee can filled with EOS and 10w-30 engine oil and let the lifters bathe in it until I'm ready to put them in.