If you have a two door 1966 Impala Convertible that "8" in 16867 is actually a "3". The R indicates that it left the JANesville WI factory back in the first week of November painted "Regal Red" and had a black convertible top at that time. The 813 tells me that you had a Black vinyl bucket seat interior in the car (generally an indication that it was a factory built SS). The 2MR and my coffee ground reading indicates that it had the optional PowerGlide transmission instead of the base manual three speed, a rear seat speaker.
You should be warned that ever time I decipher a cowl code there are a handful of members that clammer for my head for spreading false information. I just report what I have found in my books covering Cowl Tag Codes.
Thankyou big dave, It's red with white interior, buckets and that's sounds like my girl. I have a car that is completely tore down and I just started my inventory. The fenders have the ss badges but no motor size. I was hoping for that to pop up on the tag
GM never included the motor size. Only occasionally did they indicate a V-8 over the standard six cylinder; but even that info could be wrong, as the cowl tag was attached to the car body before the car was built. The VIN is the definitive source of info in any discrepancy because it was the last piece of documentation that was permanently attached the car.