Casting numbers on a BOSS 302 blocks: should be C80E-6015-B, C8FE-6015-B for early '69. C9ZE-6015A or B or D0ZE-6015-A for '69. D0ZE-6015-B or C for '70. D1ZE-6015-B for a service block.
These casting numbers are hidden behind the starter.
An easy preliminary test is does it have screw in freeze plugs?

