there one other place to try is
www.mustangdepot.com they have suspension kit you can buy and reasonable on price. The kits can come with front and rear or separately.
With leaf spring choice I have 5 leaf race leafs with mid eye 1" drop and mine ride great. But the 4 to 4 1/2 leaf would probably be best for you for cruising. My buddy got koni adjustables for my car and I dont know where he got them from. I can adjust them soft, medium, or firm. But my kit came with the kyb shocks.
ross