I run Intense'* LS style retainers with 130# springs. No problems or issues.
Comp Cam springs were breaking since they've moved production to Mexico a little over a year back. LS6 springs apparently break often on Vettes and most 3800 guys haven't noticed it yet. And ZZP retainers are milled, I've seen a couple guys that had issues with stock rockers scuffing them. It'* probably a lock/retainer combination that hasn't been documented much. But there can be an issue.
If I were buying. I'd pick the stuff up from Intense and get Crowe 105# springs as they are easiest on the timing chain and their LS style retainers. Valve seals are a good idea at the same time, buy those from ZZP and not Intense. I was unable to install the Intense ones. Pretty sure Dan fought them as well.
00 Regal GS: All kinds of cool stuff.