Go for the longer shock and use correct bumpstops to limit uptravel - you may not think you need the flex now, but you will like the droop for travel whether you do rocks or run across the desert.
If you're putting a set of 33-35" tires to suit the lift, you'll run out of fender clearance before you bottom out the shocks unless you trim super aggressively.
'00 XJ Sport, White - almost done for now...
'11 Town and Country - people mover :-(
'88 XJ Up Country, '01 XJ Sport, '08 KK Limited, '98 XJ Parts Donor, '07 XK Limited (the Stall-ander)