Raiden; You have an L Pantera and there should be no significant difference in value.
Your vehicle is pictured in the Pantera Registry (www.provamo.com). And, as you state, it appears your vehicle was built in Oct. 1973. Your title should be the official model year. Go to Ownership Issues Forum on this website and find "Pantera Production History" which will help you understand Pantera production and serial number designation with model year. There were carryover '72's sold as '73s and late 73 productin sold as '74s. From what has been discussed on this forum and in other publications, Ford and Detomaso Pantera constantly were having issues with when the car was built vs what model year designation it had. In '72 the U.S. manufacturers were somewhat consistent in introducing the following years model in the fall preceeding the calender year. Seemingly, Panteras, by the time they were produced, serialized, model year became somewhat vague, other than once it was determined that a certain serial number started a model year, the following VIN's became that model year.