ALso keep in mind that the bump stop protects your SHOCK ABSORBER...if you don't have enough bump stop length and 'stuff' that tire, if the shock is not long enough...
you will either force the oil out of the shock destroying it, or drive the shock right up through the mount when it bottoms out...destroying both the shock and the mount!
It doesn't hurt to have 'longer' shocks than needed, but it IS critical to have the bumpstops.
I am not an expert mechanic...not a clue about most of the stuff, but I would think if you measured the length of the original bumpstop and then add a lift kit-you would want a bump stop with same additional length (lift) added? I have a pair of new, unused bump stops to fit my YJ...and they are 5" long...for 2.5" lift. Seems to me when we dissasembled the original and took it off the frame the stock bump stops were only about 3"...hopefully one of the real hard core jeep guys will jump in and correct me if wrong!