[outfield]

By the look of the stance of your Burb I would say is has a 6 inch lift. The front must be all springs, which I see it is. The rear can be all springs, or blocks and springs as needed. Definitely take a picture or two of the rear set up and we can see what you have. An add a leaf is uaually a sorter thick leaf found near the bottom of the spring pack. All the stock leaves will be the same thickness, except the bottom overload spring.