We sort of started to cover this. "Hard on the bearings" implies that more force is being placed on the inner bearings, because of the perpendicular distance the tire is from the bearing. However, there is only 1" difference between the tire's position (as compared to the furthest bearing) for the rears as is stock for the front. Granted, several thousand pounds of force offset by an inch results in several hundred more pounds of pressure from the moment increase - but think of the crazy loads and stresses put on the bearings by driving fully loaded offroad with a 30 degree horizontal slope!! As gerhard mentioned in another thread: old grease, moisture or grit are far more likely to do damage to the bearings.
Mark - Part of the reason the back looks wierd is because the box is too wide, or looks that way. That's why the M135 and M34 beds are 88" wide - they line up with the running boards of the truck.
Matt