Need help with value of 67 firebird

[Firebird one]

Hi just wondering if I could get some expert advice on the value of my mother-in-law's car. Thank you in advance. She just recently got to a nursing home so she has to sell.
It's a one owner 1967 firebird 326. Has approximately 120000 miles. Convertible. Everything is original including paint. Has original warranty purchase title paperwork. It's been sitting for at least 20 years. Does start and drive. Just has the single dent.Thank you in advance for your help.