The Big Motor 1977 RS models had 40mm head pipes and big intake valves, and made a fun ride. Had one, blew it up running unleaded gas on old heads and sold it, big mistake.
I understand that BMW was forced to sell 1977 RS models in California, Florida and Oregon (i.e. CFO) with lower power output, a pollution issue, I suppose.
I'm looking for a project Big Motor 77 RS and don't want to get stuck with a CFO model. What are the ways to tell if it is a CFO? Measure the head pipes? Is there a 'CFO' marking somewhere, like in the VIN? Any other foolproof clues?