I've had the pleasure of Owning 3 rubicons; 04 with 42rle, 04 with Nv3550 ( loved it) 06 LJ had the NSG370 6spd ( hated it) was so noisy. i would never own another!. That 5 spd tho was a blast. 03-04 is the 3550 05-06 is the G370
the only thing you have to do is swap out the bell housing typically like 100 bucks used.