60 chevy VIN on frame
The entire VIN was in three locations on my dad's 60 impala convertible, all on the top of the driver side frame rail:
Location 1: Above the steering box
Location 2: Under the drivers seat above the area where the stock muffler would be located
Location 3: Under the trunk floor about 2 feet in front of the back of the frame
Granted, it was hard to read in some areas due to rust, but it was there. You might need to make one "soft" pass with an OD sander to level the rust on your frame and then, depending on how bad your frame is, you should be able to see some or all of the number impressions.
Good luck.
Doc