Not the engine, but a partial VIN is stamped on the passenger's side of your transmission. It is unlikely that if a previous owner removed the original engine they would have replaced it with another 2.8L power plant. Most swaps would have upped the vehicle power and gone to something bigger. If the trans has a different number than is on your windshield label, its a good bet that both the engine and trans were swapped out from the originals.

 

Partial VINs (last digits) of the car are stamped on the engine. Atleast on the V8s. Would think the V6 is no different. Look around the front near the water pump for it to be stamped on the pad. Most likely it will be covered with dirt, grease, etc.