I'm with the guys suggesting that you put axle stands under the FRAME rails first. That will put the car's body in a 'solid' frame setting.
Once this is done, you could apply a little pressure on the axle tube itself, aim for the side you are actually dropping the front spring hanger. Once you have this in place go ahead and un-do the main front bushing bolt, then un-do the 4 nuts that actually keep the hanger bolted to the body.
The leaf may want to move up/down on you a bit, it really depends on the clearance the particular parts have right now...but either way, it shouldn't be too big for you not to be able to correct it and hook it back up to your new hanger.
I'm curious, is the front bushing round or oval? I ask b/c Mopar switched to the oval style bushing to help with ride quality, etc....obviously, the round style is a much harshes bushing, but it does do a better job keeping the suspension pieces where they need to be in order to move the car....