Mine are from 2000 so they were the pre-LS1 style valvetrain. I adopted my "old" heads to the "new" valvetrain technology. I did it to get mass out of the valvetrain which was especially important to me because my heads are pedestal mount and I wanted to get as much stress off of that 5/16" bolt as I could. The only thing I retained from the "old" style was the valves as I didn't make the switch to the 8mm setup as it would have required way too much work. The springs, locks, retainers, seals, and spring cups all needed to be changed but it wasn't hard. The only semi-diffcult problem I ran into was that I needed to have the head cut down a little where the spring pocket sits in order for me to get the proper installed height. I also had to run .050"+ locks to help get the installed height correct and to ensure I had enough but not too much spring pressure.
The reason everything needs to be changed is because the older style springs were around 1.4X" in diameter, and the LS1 style are 1.2X" in diameter. This is the reason it all needs changed.