very nice to find this Heuer in the Shelby!!
values on these vary considerably, but $1,000 would be a nice round number, to use as an estimate / starting point. Keys to the value are whether the dial is clean / pristine, whether the hands and luminous have stayed clean and bright, and whether the movement is in good condition. If all these factors are favorable, and it had recent service, value could be closer to $1,500. (For it to run well after so many years, it will likely require an overhaul, which can be a $200 to $300 ticket.)
Send me photos of the Sebring, and I can tell you more. Also, feel free to send photos of the Shelby!!
Thanks for posting your inquiry.
Jeff