I beleive the number might be stamped on the frame as well, somewhere on the top of the left side frame rail near the steering box. Don't quote me on that, though. I know that it is on the '55-'59 trucks, not 100% sure on the earlier trucks.
There are no numbers on a '55 first and earlier Chevrolet frame. Some '55 second reportedly have them. All '56-'59 do.
