What to do with a 65 Valiant that won't sell

A couple of options.
Believe it or not nobody is born knowing how to weld.
Get a mig welder and practice on scrap metal until you get the knack of it and then weld up your floor holes. A 4 door valiant is a perfect car for first time hobby welders.

The other option is to cut up and part the car out.
Frame rails etc are probably good enough to sell.