Yes, I think what I'm looking for is a 4-digit alphanumeric stamped into the oil filter canister but I didn't see anything other then the full engine VIN. It's possible that its somewhere on there that I can't see from under the hood.

Thanks for the picture Oldblue! That makes me wonder if that bolt sticking out of the top of my heater hose is suppose to go directly into the block. When the engine cools off I think I'll take the hose clamps off and inspect it.

I called a local Chevy Dealership today about having them check the Engine Vin# to find what car the motor came out of. They said that it was something too difficult at the dealer level to do and that my best bet is to call General Motors customer support.

 

Here's a thought. Good that be used for a vent or flush connection.
When doing a coolant flush?

 

That bolt will let coolant out! and yes it can be used as a vent to let air out while filling the block with coolant