1970 Dart GT Value?

I doubt that it will be much more valuable than a comparable Swinger. That means an original 318 Swinger, however, I would think that the 340 would add some value over and above that. I would agree with @GTX JOHN on th $20k, and I base that on what I sold my 70 Dart Custom for several years ago. It was a 318/904 bench seat car, upgraded to 360/727 with cloth buckets and console, floor shift, 8 3/4 with a sure grip and 3.23 gears, never had any major rust, body and paint were 8/10. The car ran and drove perfectly and was extremely reliable. I sold it in 2011 for $13,500.00 CAD, which was about $12,700.00 USD at the time.