Is there a way to convert a 65 dart post to no post ??

I can't answer your question but I know this has been done on '66 Valiants. The '66 Valiants all use same roof panel; 2 & 4 door, sedan & post are all the same. Not sure if the Dart shared the roof, if so it's do-able, especially if you can find a parts car.

A Mopar parts book or a Glenn Mitchell collision repair book would be a good guide for this.

Yes the auto makers did go to all of the trouble to make sportier Hardtops, even on four door and station wagon models. With car design appearance trumps everything else, which is like many things in life.