I'm not an engineer, but it seems to me monoleaf springs on an otherwise stock AD truck would increase the body roll due to reduced spring rate, and you wouldn't be able to corner at all. These rigs are all steel, and weigh a couple tons empty (mine is a 3.5 ton panel, GVW 8800 lbs). Unless you NEVER carry any weight and add heavy swaybars, the monoleaf springs will break the first time you swerve around a dog in the road. I'm sure you can add hardware to compensate, but that will push the cost up. Again, I'm not an engineer and I may be off-base, but I prefer to err on the side of safety.
If the objective is to lower the truck a few inches, lowering blocks can be installed on all four corners, and the only loss will be spring travel (not an issue if the truck is just for cruising). New shocks would be a good idea, since you're changing the height and the throw; and depending on how low you go, you'll need to alter the steering linkage to keep it from binding. If you're trying to get the nose in the weeds, you need to junk the straight axle and find an IFS clip to make it safe.
[small]"Pass the cutting torch, I'm done f***ing around." -hedgehog[/small]
