Where's the dipstick? If it's closer to the starter, then you have a 51-5 engine. If it's closer to the oil fill tube, it's an early engine.
Also, one thing to note, a stick shift engine will not work in a hydramatic car unless you swap crankshafts. The auto trans has an end that sticks out that fits into a hole in the crank. Stick engines do not have that type crank.