It shouldn't be too much more difficult that the Calmini 3" body lift.
Like Zukipilot said, there are many things that must be extended. The shifters (t-case and transmission; if you have a 5 spd), the gas filler and vent, the steering shaft, etc.
One thing you need to keep in mind is that the back 6 body mounts have fixed studs, meaning that you'll have to use a 1" spacer on top of a 3" piece of square tubing to get 4". The front two will require new, longer bolts, and a few hockey pucks stacked up would probably work up there.