I have a 2001 LS 430 and the airshock system is failing. I've read a bit about converting to std shocks and have found 3 websites touting their kits but have no idea which is the best, or if they're comparable, or what. My mechanic is unfamiliar with the various sites and though this is not supposed to be a difficult conversion, I'd like to get the best one for ride and longevity. Any help?