I'm guessing you are trying to cycle them after they have been stored on their side or possibly upside down. Put them in their proper orientation and after a few cycles the gas will get to where it is supposed to be and the shocks will function properly
If your not looking for added flex and/or durability offroad they aren't necessary until you start getting driveshaft vibration, and even that can likely be fixed for less money with a carrier bearing spacer.
The mojave/rubicons sit taller then other models but the shocks aren't any longer.
You can run the mojave shocks and just spacers no problem, it is just a less ideal setup. Extending the bump stops and shock mounts will give you better compression/droop setup and also make room for larger...