How can you tell if you have a Chevy 305 or 350 engine?

YOU CAN EITHER TELL BY THE HARMONIC BALANCER THE 350 IS THICKER THAN THE 305 OR YOU CAN TELL BY LOOKING ON THE BLOCK ON THE FRONT OF THE PASS SIDE HEAD THERE IS A FLAT SPOT ON THE BLOCK THERE SHOULD BE SOME NUMBERS AND LETTERS FIND THE LETTERS AND CALL A PARTS STORE