How much travel should a shock have?

[Olden Days]

I recently bought used 2 inch lift springs with rancho shocks. I installed springs and went to put on the shocks which I double checked (on their website) the part# for being correct for 0 - 2 " lift and had to extend them completly to get them on with no room at all left for more extention. I dont believe that could be right so I ordered some skyjackers that claim to be for 2 -4 inch lift. well I went to install and had to compress them to where there is only 2" left for downward travel. I dont believe that could right either. So how much travel should one have in both directions ???? how can I find the right ones??? thanks Jerry