you can't get them in the US, only as a grey market, there is a company in UK that sells them new and used, i need to dig up that info... The E53 comes only as a 4.4, not as 4.6 or 4.8, the driving dynamics are slightly different,as you are hauling several hundred pounds of extra weight, you lose some features, like folding rear seats, as the rear is reinforced. You get the external PA system to communicate with the folks outside, you can turn off the airbag function, and use the car as a ram, the tires are not just ranflats, the rims have a plastic "tire" installed inside on the rim and then the rubber tire is mounted over the plastic one - in case of a gunfire damage, the rubber tire disintegrates and the car continues to operate on the plastic tire, the exhaust has an anti-potato grill, that prevents somebody plugging the tail pipe and thus preventing the engine from running...

the price of those cars is about three times of the regular retail of the comparable retail model...