340 compression ratio

IF STOCK PISTONS, they will come up over the block. And stock CR on the early build 1971 340 is 10.25, where 1970 and earlier is 10.5? What I read somewhere...... My 340 is a late 1970, so I'm guessing it went into a 1971 car. Just guessing, when I get around to it I will find out for sure.
Yessir, I’ve read that before too. I was just trying to see how close I could figure it. I don’t think it’s stock/factory pistons in it. Wanted to be sure before I order my head gaskets to make sure I get the right ones. Plus I’d just kinda like to know what it is when I put it all back together. Thank you very much for the info.