[mmiddle]

A 307 was a 283 bore with a 327 crank. 3.875 bore & 3.25 stroke. This made for more torque than the 283, but less potential than the 327. Overall these were a base-line engines and have never been popular for performance because of the odd CID. And chances are you cannot bore these blocks out to a 4.00 bore of a 302/327/350. You are better off finding a 4" bore block and starting from there.

Conversly, a 302 is a little monster. Lower torque, but very high RPM and very quick revving potential making it perfect for the short track in a lighter car