On early models there should be a VIN tag that will tell you almost anything you need to know, at least my chevy's did. I had a 66 Chevelle the VIN tag told told me that it was a coupe and should have a 327 engine, hydroglide trans and it was originally painted forest green. Not only that it will even tell you the month and week it was built. Looking at the vehicle comfirmed these few listed items, it came with split buckets and a center shift console with the dual bar lever, had no window frames, just not having window frames in itself denotes that it is a coupe, which is the platform a SS is made from. It's been a long time since I was into retro cars and would really have to bone-up on the codes within the tags but I was able to narrow down what I had by that tag. Not all the info on old cars came within the VIN # itself so you have to read and decifer those extra numbers and letters on the tag that don't have anything to do with the VIN itself.
My Chevy Elcamino told me it was a SS 454 with a 4 speed,color was black and it was a stripe delete. Sadly when I got it the 454 and the trans were long gone.