From the photos, it looks like you have about an inch of up travel, but it's kinda of hard to tell. Nevertheless, you need some additional travel. It's unlikely you can travel much further up prior to the diff hitting the cross member. Ideally, the bump stop hits just prior to that happening. So, to get more travel, you need to increase the distance to the bump stop at rest. The best way to do this is to increase the arc in the springs. You could simply add an additional leaf or two, but that would increase the spring rate (how much force is needed to deflect the spring upward ) resulting in a harsher ride. Ideally springs are designed for the weight of each axle eliminating any excessive rate. So, for additional travel and a better ride, a set of springs designed for your axle weight and desired lift height will help eliminate excessive bottoming, but other factors come into play too. Increased lift height may require longer shocks. You could also install softer, more progressive bump stops, but that wouldn't increase the travel any.
Agile Ride improvement package