Have you decoded the fender tag thoroughly??
Did it ever have a vinyl top?
I find it odd to have rust bubbles on the top drip rail and never anywhere else.
Have you got under car and looked behind the bottom rear quarters?
The added side molding and wrong stripe bugs me. IF it’s all stick on molding it can be removed. But it might lift paint. And it might leave a shadow of non sun exposed paint to exposed to sun paint.
Is the stripe painted on? It’s wrong for 69 GTS and I think in the wrong location some.
I think a safe buy is in the $15K+-ish range.
Will you live with the paint the way it is ?
If you paint it, paying $20k+ is not worth it.
