Sounds like you have tried everything but I would check the bind in the shackle bushings. Did you install urethyene bushings in the bottom of the shackle? Sometimes the urethyne bushings get in a bind so you have to loosen the bolt and then make sure you put lock tight on the nut so it won't back off. Also you may know this but make sure your shackle bolts are loose when you let the car down off the jack stands then tighten the shackle bolts. If that's all OK then it must be a lazy spring in the front or rear. Jack up the front of the car and see if it still leans. If it does I'd say it's a lazy leaf spring. I assume you have stock suspension? Could be your shackle bolts are too tight.
I had the same problem on my 67 it was a lazy rear leaf spring. I had to change it out 4 times before I got a good spring. Sounds funny but it's true.