A cubic yard of stone can vary between 1 and 2.5 tons. It all depends on the type.
The maximum payload, as far as I can tell, of a 2007 ST is 1.39 to 1.45 tons. You should check your manual to confirm.
If you're bagging it, find out the weight of the bags and stay under the limit (and don't run up against it; give a buffer).
If you're getting it in bulk, make sure the guy with the Bobcat knows his bucket size, and always err on the side of less. (I would not recommend anything larger loading as you'll end up washing your ST with rock unless the guy is a great operator.)
If you're trailering it, simply keep in mind the capacity of your trailer as you would if getting it in bulk.
Getting about a ton of #57 stone: