how to tell if engine was changed
 

OK, so the po of the suburban said he changed the motor, how can I find out if he's telling the truth or not? It is a 90 suburban 350tbi where would I need to look to find the vin or some sort of identifier. As always thanks in advance it is greatly appreciated.

Re: how to tell if engine was changed
 

The VIN is all over the place on these trucks. On the dash viewable from the windshield and one on the driver door are really easy to spot.

On my truck they swapped the 305 for a 350. Of course I have all the paperwork showing it was changed, and my VIN indicates a 305.

Re: how to tell if engine was changed
 

Look here for casting code and other block codes to check your numbers.
http://www.mortec.com/

And here might help too.
http://www.nastyz28.com/decode.php