Hello!

long story short, i'm thinking of upgrading my valve springs, seen that i'm boosted (xcharger xtreme), and i've read that the nissan 909 are the way to go..can someone point me in the right direction?maybe with a part # or a web site where i can buy them?..also, i was wandering if they're still produced or not nowadays..if not, what are the "successors"?