The heads are the same but the valves and valve springs are different. the '01 uses LS1 valves whereas the newer heads use slightly longer and lighter titanium valves. The springs are identified by the color. I believe the '01 springs are yellow and the newer ones blue but I could have that wrong.
Visually other than the spring color, which I've heard is really not consistent in color or application, how do you tell them apart. Are there casting bumps, printed on parts numbers, etc. I'm looking at buying a pair and don't want to end up getting 2001 heads.
The original springs have a paint dot color code on them, unfortunately I don't remember the colors well enough to advise you. Do a search over on LS1Tech.com as well, this information is likely found there. This is of course assuming that the original springs are still on the head. Not sure what the visual differences are in the valves, but a quick e-mail to Bob at Precision Porting will likely provide some information on the valves as well. Good luck