The Sprint package was available to all three body styles; coupe, convertible, and fastback. I have a Sprint convertible. The fastback is the rarest.
All Sprints will have the chrome air cleaner, wire wheel covers, console, and pinstripping with the quarter accent trim delete. It was part of the package. Package A included the base 3-speed manual transmission for $39.63 retail and Package B included the automatic transmission for $163.40. You could also upgrade your Sprint, just as you could any other Mustang, by ordering a Pony interior or wood wheel.
It’s possible that a previous owner may have simply placed a chrome Sprint air cleaner on your car if it doesn’t have the wire wheel covers, console and pinstripping. Or the wheel covers were replaced with another style, the console was removed and the pinstripe covered over by a re-paint. If the car has the 3-fingered quarter accent trim, then the chances are that it never was a Sprint. Sprints wouldn’t have had the trim. If it doesn’t have the trim then it may be possible that the other identifying features were removed. You’d have to remove the interior quarter trim and peer into the quarter panel area where the trim attaches to be sure that it never had any holes. Once you can confirm that, you’d have to inspect the transmission hump to see if there are any holes from the console.
You might also look for a build sheet. I found mine taped to the wire harness behind the speedometer. My research on build sheets seems to indicate the possible presence of a code in the last line, sixth box from the right.