The other thing to remember with pretty much all dinosaurs was that they had bird-like breathing systems, involving air sacs. This meant that the volume of the animal that was air would have been far greater than it is on a comparably sized mammal, which further reduces the weight. Birds usually have hollow, air-filled bones and indeed evidence of air cavities in the bones of dinosaurs including sauropods has also been found, even extending to the spinal column as well as the major limb bones.
If you do the lung volume estimations, an air-sac based breathing system is the only way something the size of a sauropod could muster enough tidal volume to be able to breathe efficiently enough to survive, so they absolutely must have been using this system.
Finally, although sauropods had brain volumes right on the reptile brain to body size ratio, they were assuredly not "cold blooded". In fact, they probably had more problem keeping their body temperature down rather than keeping it up, as a herbivore that size would have several tonnes of fermenting plant material in its gut, which tends to generate a sizeable amount of heat. This BTW is why you very seldom see cows shivering; their gut fermentation processes generate more than enough heat to keep them warm. The gut fermentation is also why big bovids always keep on looking for food right through extremely cold winters; the animal its self isn't getting much nutrition off the forage, but it needs to keep on feeding the bacterial colonies throughout its gut to keep everything in good order.