Driver's side rear quarter, under the weatherstrip. You are only going to get "BO123456" or not a "B" depending on where the car was made. We had the SAME scenario a few times back in the 80's at wrecking yards - one was a Moulin Rouge '70 GTX in TX, the other mystery car was a butterscotch 71 Cuda in CA. Never knew what either car had for drivetrain.