On both my Ranger and my F-150 I custom built rear leaf packs. IIRC both have 5-leaf packs now with overloads on the bottom and neither have a bad ride empty. The key is to build the pack with the longest leafs possible - the longer the leaf, the softer the ride. By adding additional leafs, you also increase your hauling capacity.
My Ranger gained about 2" in the rear with the "new" spring pack (I had to use 4x4 shocks because the stock 2wd ones were too short). With 1,000# in the bed it would sit about level, and at 2,000# I was still slightly off the bump stops.
My F-150 gained about 3" out the back but the stock shocks seem to work just fine. It looked kinda strange on my F-150 till I replaced my front coils with heavy duty ones, which brought the front up about an inch or so. It sits level with 2,000# or so in it. I'm still thinking of adding factory style helper springs though.
Air bags or factory style helper springs also help with load carrying. The factory style helper springs attach where the U-bolts hold the spring and axle together and go up to frame mounts above your leaf springs. Depending on the style they either just lightly touch the frame mounts when empty or sit just an inch or so away from the frame mounts when empty. When loaded, they contact the frame mounts and it's like having an extra spring pack on each side. I had toyed with the idea of doing that to my Ranger, but decided that it just wasn't worth it, if I have to haul more than 1,500# or so, I have the ability to just use a bigger truck.