JTEC = Jeep Truck Engine Controller, one of the first-generation OBD2 computers used by Mopar. As the name implies, mostly used on Jeeps and trucks... and the Viper. Fairly rudimentary setup by even contemporary standards. 97-04 TJs all have JTEC.
NGC = Next Generation Controller, used on a wider variety of models. It requires more accurate knowledge of where the cam and crank are, so it needs cam and crank trigger wheels with more teeth. 05-06 TJs are the only vehicle ever made with the combination of the 4.0 and NGC, which probably explains a lot of the "unique" parts that 05-06 owners have to deal with.
Since the 4.0 crank trigger wheel is part of the flexplate/flywheel, that trigger wheel needs to match the computer in the vehicle. And since Jezza's adapter fits within a JTEC flexplate, that results in the extra work shown here to create a NGC trigger wheel that mounts to the JTEC flexplate.