I am wondering if I can set up my windows like I said in the title. This is for a 1972 Dodge Demon.
Any help is appreciated.

Thank you in advanced................Ted

sure, just use your rear lap belts, take out the window regulators ,slide the belt down between the glass and door, bolt latch half to bottom of door

Bear in mind that the belt-setup cars had lightweight glass, and wear on the UDF paint from the belt most likely wasn't a concern.
That said, it would be worth mocking up to see if you're happy with that setup.
Disconnect the glass from the regulator, bolt up a seatbelt to the glass channel, & pull it up.
Might have to modify or eliminate the inner window sweep.
Then figure out a buckle mount on the door.
"Helicopter tape" or "ClearBra" on the UDF would help preserve the the paint.
Not sure what those regulators weigh, meaning if it would all be worthwhile.

What I ended up doing on my Dart project was to go to a pick-a-part yard and find nice rear seat belts that were very soft and flexible. The originals from the Dart were just too stiff and there was a lot of difference between ones in different cars. I figured that softer and slicker would be easier to work with and less likely to scuff the door's paint. I didn't put any protection where the belt rubbed the door paint. I just didn't pull the belt across the paint. The belt was only against the paint when it was snapped. And I had put a couple extra coats of paint on the top of the door in anticipation of some potential belt wear.

The other thing I ended up doing was that I didn't attach the seat belt directly to the bottom of the glass. I used a bungy cord that attached to 2 places on the bottom of the glass and then attached the belt to that loop. That way I could have some upward pressure on the glass when up and still have enough 'give' to get the belt snapped into place. Besides, should the belt stretch some, the stretch in the cord would still take up the new slack.

I had to experiment with different bungy cords to get the right tension and length, but was no big deal. They are certainly cheap enough.

Oh, and you can order door panels from Legendary with no window crank holes, if you want to go that far.

Mine uses straps from a plastic battery box. Snap at the top when the window is down. Snap on the bottom to hold the window up. It is a B body but the principle is the same.
Doug