You'll need to take measurements to figure out what shocks will work best for you. Also try to determine what up travel and down travel you want. To make it as simple as possible, measure your shock right now at ride height. Then go look up your desired shock and pick the one that will be in the middle of the shock travel (roughly half way between extended and collapsed lengths) that matches your current shock length at ride height.
From there, it's really a matter of how much work you want to do to make improvements. It's possible your current shocks are limiting your travel unnecessarily. Or it's possible that there are other suspension components that are limiting your articulation, so buying shocks and doing work to use more travel would be a waste without replacing those other components. There's a lot of research you can do if you're looking to change things up to make room for more suspension travel. It won't be as easy as picking 4" lift shocks or 2" lift shocks. Also, you won't know exact bump stop numbers until you're all put together. We'll help where we can.