being a 383 S car significantly increases the likelihood that it's still around.
i bet if you included more detail the higher the chances are that somebody may remember it or have seen it.
for example, if i was looking to track down a car this is how i would go about it:
my name is John Smith, i'm looking for a 1968 383 Formula S barracuda in B5 blue with white interior i used to own between 1975 and 1986. at the time i lived in Anytown USA and frequently traveled to This Other Town and to these types of car shows and raced it frequently at This other other town track. in 1986 i sold the car at carlisle to a gentleman from [blank town] mass. i've since talked to him, and he's since sold in 1996 to a guy name Jack Smith in [other town] mass.
here are the details: 1968 Barracuda Formula S 383, 727 AT, manual steering, manual drums, at the time it had ansen mag slots. i installed hooker headers and a holley. it was B5 blue with white deluxe interior. there was hole in the headliner just behind the passengers seat that got put there by heels from the girl i was dating at the time. i had a pioneer radio in the dash and a supershops sticker in the driver's quarter window. the license plate was 123-abc and the VIN was [blank].
here are some photos of when i owned it, here are some photos from the guy i sold it to. it's last known whereabouts were: [include details here]
sometimes to catch a fish you gotta cast a wide net