1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
Frame ser # stamping
The ser # on the frame is located on top of the left side rail under the drivers seat area or a little forward of that. I have seen posts on the NCRS stating a more precise location but also it was relative to where the guy stamping it placed the stamp. You will have to use a mirror to view the top of the frame rail. Your success will depend on how clean your frame is. Some have had to raise the body a little and sand the top of the frame to get the stamping to show up.
I have never looked for mine but I have no doubt that is is original.