We had some issues with that. We thought it would be lifted already, the springs we used were 4" front lift springs from the 40 in the background of this pic:
Those are 6" on center shackles, mounted almost vertically with little weight on the frame. The weight of the box flattened them right out and now the spring eye hits the frame and the shackle is laid all the way back. We are going to install a new spring hanger in front of the old one and probably some short/cheap coil over shocks.