I have contemplated the reasoning for the differences between these two applications since before 1995 when a few of the LVS's were for sale. Now that I have one and have crawled underneath them.....my thoughts are that essentially the axles are the same and my gut tells me that originally the LVS was designed way back with the "standard" 1600/20's. But as the weight capacity of the LVS grew, and because of the partial "skid steering" of the front end (#2 axle does not steer at all), I would not be surprised if the LVS's were tearing the tires right off of the rims when planted in soft ground at full weight capacity. If you look at the front axle leaf spring "perches", they each have an extension to the casting which rides along the side of the truck frame as the axles contort with the terrain. I assume these are also to keep the axles from being ripped out from under the truck during horizontal articulation, which leads to confirming the extreme side forces I am talking about. So for the tires, it was simply a matter of creating a "deeper" bead on the rim on the backside and widening the "ring" on the front side. This also offered enough space on the front "ring" to attach some nuts to allow the 3 "keeper plates" to "lock" the ring in position so that those lateral forces would not as easily dislodge the "ring" and wreak havoc on the tube and tire. To do this there were basically 2 options - keep the tire size and make the axle/hub assembly smaller in diameter (much more expensive), or just add the 1/2 inch to the outside diameter of the rim to achieve the above changes (seems a bit more straight forward - there was not going to be that many of the trucks anyways compared to the HEMTT series, so some custom rims and tires were a simple fix). Just my thoughts on how this probably all came to pass.