Hey guys I had some guy give me a set of pistons out of a 3970010 block and I was wondering what compression they would be at with a 64cc head?? any of you guys know? they are slightly dished.. I am thinking at least 9.0:1....

 

If they're the typical stock ones, you'd end up with about 9¼:1 with them.

But who in his right mind would build a new engine with a bunch of old stock garbage cast pistons anyway... it's really a moot point. They're the same trash that came in any 350 built out of any other casting. The block casting number doesn't somehow magically imbue the horse-dung parts inside it with some sort of superior properties that remain in effect after the parts have been removed.