Early Valiant with XHD leaf sprAngs.

Nice to know someone else out there appreciates a good muscle car stance and doesn't want to lower it to the weeds and look like an idiot.

When I first got my 68 dart I cranked the torsion bars 17 turns up on each side and put some spring extender thingies to raise the rear.

Really Rainy? Spring extender thingies? Did you mean longer rear spring shackles?
Never a good idea on a Mopar. As you found out the rear springs soon take on a reverse arch and you defeat your intended purpose. Mopar engineers did a good job on the rear spring geometry but for some reason people think they can do it better.
What's next air shocks front and rear?