They all say Hi Perf. on them in that line, even the peanut port truck heads. But you have a good combo there, although the heads have pretty big intake runners for the street (327cc) Depends what you want to do with it. I ran them on the street for a long time, it was good, I just lost a little torque cause the flow velocity with those big runners is slower. They are a high RPM head, but make no mistake, they work great. I see them selling for quite big bucks too, that's why Im hanging on to mine. Good luck with it! Two really good books that I use all the time are HP's "Big Block Chevy High Performance", by Dave Emanuel.....and CarTechs "How to Build Max Performance Chevy Rat Motors", by Ed Staffel. There is also a good book with codes in it, I think it's "Chevy by the Numbers" or something like that. I got mine at a regular book store, maybe Barnes and Noble, or Borders. Or you can order them from Amazon.com, or Summit or Jegs has them too. John