What year is a 350 Chevy engine with casting no 3970010?

The casting number 3970010 is for a 1969-1970 350 cubic inch Chevrolet small-block engine. However, the casting number alone doesn't definitively pinpoint the *exact* year of manufacture. The engine could have been cast in late '69 and installed in a '70 vehicle, or vice versa. You'd need additional information, like the vehicle it came from or a more precise date code stamped on the block itself, to get a more precise year.