I don't quite understand what you are asking about "year model". You said it was a 1990. If you want to know what "model" it came from, that can be a little difficult. There should be numbers on the motor somewhere that can possibly give an idea but it is just a guess.joecurry said:I bought a 1990 GMC 1500 and I was told that the motor and transmission came out of a Yukon, they didn't know what year model it was. Can some one tell me how to tell what year model it is. It would help me out alot.