How rare is a 64 Fairlane 500 Sport Coupe?
Not very. There were 277,000 or so 1964 Fairlanes assembled. Of which about 21,000 were 65B models, Fairlane 500 Sport Coupes with bucket seats.
There were two 289-4V engines available in the 64 Fairlane, the 210 hp R code and the 271 hp K code. There were 600 K code Fairlanes assembled in 1964. Interestingly, the K code motor was available at the beginning of the 1964 model year, but not installed in the Mustang until June. IIRC, the 273-4V was an A-body only motor that did not come out until the 1965 model year.
Shelby's modifications to the K code produced 306 hp naturally aspirated in the GT 350 and 390 hp with a Paxton supercharger. The K code motor was very pricey because of all the tweaks Ford put into it to get the power out. It was phased out because the 390 and 428 produced similar horsepower, more torque, and were easier to live with for far less cost per unit than the K code. (Also added a bunch more weight on the nose of the car.)
For a little perspective on the situation at Ford, Dodge built 39,000 Demons in the 1972 model year, 8,900 had the 340 or had model code LM. Because Chrysler did not assign a different code in the VIN, it is not for me to know how many had buckets or bench seats. The trim code on the body code plate does contain that information. I was unable to locate any presentation of totals that would be useful. Govier only tracks engine/transmission/make/model combinations for the most part. I do know, courtesy of Govier, that in model year 1972, Dodge built 97 Demon 340s with a folding canvas sunroof. (Code V3?, with the ? being the color for the top.)
