Undecided.... sell it or not

I have a guy coming out to look at my 70 Dart Pro street car. He's been asking about buying my car for two years now. He's got money and agreed to the price...but I'm getting second thought...
I talked it over with the my girfriend and she's telling me that I would regret it in the long run and to keep it.

Anybody else has had the gitters and second guessing selling their car...

!!!I am