The XHD's will probably add some ride height. The springs that are on your car currently have no doubt sagged, and if they're 5 leaf springs they'll have sagged more than 6 leaf springs would have. So, brand new springs will add to the ride height although some of that will go away as the springs settle in. The 6 leaf springs shouldn't give you a 4x4 ride height with the stock height, but they'll almost certainly add height compared to what you have now.
The wheel rate balance on these cars is pretty car off from the factory. The torsion bars in the front were vastly undersprung, while the springs in the back weren't too far off, especially the XHD's. Going to larger torsion bars in the front will dramatically improve the barge like handling of a stock car, even if the leafs are left alone. Add XHD's and the handling will improve even more. As for the steering, if you have the stock power steering you can modify the steering pump pressure to reduce the amount of "boost" the power steering gives. Mopar action did an article on it for the Saginaw pumps, although you can do it for the federal pumps as well. Still adding spacers but the procedure for the install is different.
http://www.moparaction.com/Tech/beep/PUMP_IT_DOWN-re-v1.4.pdf
If you need to rebuild the front end add Moog 7103 offset UCA bushings, they will allow you do dial in more caster, which also reduces the boat like steering boost feeling. Alignment should be for radial tires too, not using the factory specs.