How to tell if motor is obd1 or obd2?

What is the best way to tell if a motor is obd1 or obd2 by looking at it? This is assuming it is already out of a car and sitting on a pallet... with the source of origin unknown...

Put it back into the car it came out of........................then check the DLC connector under the dash!!

see if theres alot of sensors the intake mani what car b18a/b or a c...b16a1 b16a2