Here's the difference between the 242 cases: http://www.newventuregear.com/tcases.html
I believe WJs (and I think possibly some Dodge trucks) use an NV 242HD and the Hummers use the NV 242HD AMG.
I believe WJs (and I think possibly some Dodge trucks) use an NV 242HD and the Hummers use the NV 242HD AMG.