As Devo said above with that casting number it is most likely a 350 block. The only way to tell for sure what it started out as, is by the stamped numbers on the machined boss on the block, just ahead of the #2 cylnd.. Heads might very well be 202's tho by what you say the markings are.
3970010....302.....69....4...Z-28 Camaro3970010....327.....69....2...Trucks and industrial3970010....350...69-80...2 or 4