There's 2 main places. 1 is the machined surface just behind the distributor mounting. The stamped number there will have the plant code and original application code. The other place is by the RF motor mount. That will have the block casting number, which will tell what block it is ad what years/applications it was used in. In addition, just above the starter is the block casting date, which will be reasonably close to the model year that the engine was assembled and used.

Bill Burmeister