I'm 6'5" and have the same problem. As far as I know, there aren't any kits available to lower the seats, and looking at the mounting brackets, I don't think you could modify them to lower them. The inside "legs" of the mounts aren't very long to begin with. I felt like I had more room in my TJ than I do my JK.
SOLD-08 Unlimited X, "jeep green", auto, limited slip, hushpower muffler, Aerotech Interceptor gauge,Powerstroke tranny cooler, skidrow evap skid, AFE Pro 7 filter, Teraflex leveling kit, EVO control arm skids, 15x8 Black Rock 909's, 33" KM2's