The GPV (General Purpose Vehicle) is similar to a Jeep Wrangler, but somewhere between compact and midsize, like a Toyota FJ Cruiser. The HMV (High Mobility Vehicle) is similar to a Hummer H1, but somewhere between midsize and fullsize, like a Toyota LandCruiser. Both vehicles are made to be highly customizable, down to the body panels. In that regard, the entire Jeep lineup can be constructed from one of these two frames, depending on whether it is generally large or small. The H1 and H2 are HMVs, while the H3 is a GPV.
The GPV frame will be divided into 3 boxes: the engine, cabin, and tailgate. The HMV frame will be divided into 4 boxes: the engine, fore cabin, rear cabin, and tailgate. The HMV will be wider, taller, and longer than the GPV. The frames will be built in a manner that allows boxes to be removed or added, ideal for creating stripped-down rock crawlers, limos, and God knows what else. Due to this addition/removal feature, you can effectively change the size classification of your vehicle, ranging from a Miata-esque offroadster (GPV w/ engine box and cabin box mounted above rear axle) to a Hummer limo (HMV w/ engine box, 1 cabin box for the driver, 2 cabin boxes for the rear, and a tailgate box).
The sheer potential for customization creates intruiging possibilities. Two of these possibilities, one for each frame, are illustrated here: the GPV being converted into a 40s coupe, and the HMV being converted into a 40s lead sled. Since these vehicles were from an era before unibody construction, they will ride much like the originals.