Lewguitar claims the best blocks you can get for the buck is probably the Fender vintage reissue blocks. Nice thread with somewhat scientific, step by step method to ascertain.
Callaham claims that their blocks use better quality, some say it's better, some say it's not. Fenderforum has a post with thousand over replies, quite a few experts (Callaham, Suhr, Fender) arguing last time.