My all original unmolested car may not be so original...

Find the machined pad on the block JUST under where the head meets the block, RIGHT behind and under the alternator. I would remove the alternator. Makes it SO much easier to see. You will see the numbers there. It will have the engine size stamped there.

Something like "Hay dummy 225 you shouldda done like MOPAROFFICIAL said"

LOL Sorry, I couldn't help myself.