Hey Dutchrebuild, I have an identical set of heads that came with a 1971 340 that I bought. The block is a 1971 but it has been bored 0.30 over with the double eyebrow pistons. The heads are definitely not the ones that came with the motor as I have set of early 915 J heads from another 1971 340. Someone hooked up a SP-2-P-318 intake to it with a small Holley. I guess that they were trying to get more low end torque out of it.