There is a pad on the block at the front of the right head. AC compressor and AIR pump tend to get in the way, but it's there.
There will be two numbers stamped on the pad. Larger characters will be the engine identification stamp; second (smaller characters) will be the VIN derivitive of the vehicle the engine was originally installed in. Hopefully, the VIN derivitive will match the VIN of the vehicle (plate on driver's windhsield post and visible from outside the car).
74 shown; 76 and other years are similar:
77 and later might be a bit different; 79 shown:
A VIN derivitive is also stamped on original transmissions.