I would ask tom woods how long the driveshaft can safely be. Then jack your jeep off the ground by the rear bumper till the tires are off the ground and measure it. What size lift was the DS made for originally. I had my driveshaft shortened and high speed balanced for 60 bucks, though lengthening costs more.
'03 TJ Sport
/ D30/Ford9 / 35x12.5x15 KM2 / D window black steel 15x8 wheels / 3" custom long arm lift / SYE & 1350 DS / JKS BL / 1" MML / Smittybilt's front bumper, Tube fenders, Rocker guards, and rear bumper / High Rock Tire Carrier