Where can I find the #'s on the heads to see what size engine I have? Also where are the #'s on the block? Are they on the back against the firewall? Can they be seen while the engine is IN the car?

 

the head casting number is under the valve cover, and the block number is on a pad on the deck surface in front of the left head. the head won't really tell you what engine you have, especially if it's an older engine that's been wrenched on by several people.