Using an axle with more drop is one way to lower the front of an I-beam axle truck.
I've used a later model axle under my truck that has 2" more drop than the stock one, and I've made up for it with taller springs.
If you want the drop just use the original springs and do all the work and effort to swap to the later axle.
http://www.stovebolt.com/techtips/bigbolts/p30swap/Grigg
