Charlie,
Are you trying to get the body and frame higher off the ground, or also the
axle? I can't tell since you don't say exactly why you want it higher.
If just the body and frame, you can put spacers in under the frame; if you want the axle higher too, you'd probably have to gert a new axle with a different "angle" (they come with various degrees of angle, which affect the "lift."
Raya