The issue with the valve springs is fatigue, not that they arent made stiff or strong enough. Even a quality double spring is only going to last 15,000 good miles before it's just sprung out and should be replaced. Like I said earlier in the post, its a 30 minute job for a newbie, the first time they do it, with one simple tool and a ratchet/socket. LS springs are retarded easy to replace, and on a vette its even simpler since you basically have the whole engine sitting right in front of you.