I can only comment on blocking up a skid steer in general since I am not familiar with Mustang machines. On a Bobcat the motors come out the side. They are behind an access plate between the tires.
It is always best to consult the owner/operator manual when jacking up and blocking a machine. But, not all owners have a manual.
Always start on solid level ground. It's best and safest to have a helper.
You need real good jack-stands that you have confidence in. Make sure that they more then exceed the weight of your machine. I use 22000 lb rated jack-stands that do not have any cast iron in them. I have seen high rated cast iron stands fail.
You can lift the front of the machine by tilting the bucket just high enough to get the tires off the ground and the Jack-stand under the axle tubes, close to the frame. Then raise the bucket slowly to lower the machine onto the stands.
The rear of the machine is usually jacked up with a large floor Jack. You probably shouldn't, but I have used two floor jacks, pumping one a little at a time, to lift the back of the machine. The Jack-stands should be placed at the back corners of the machine.
Just remember that if you are not comfortable with the setup that you have you probably shouldn't do it. These machine are heavier than most people realize. So make sure that your equipment can handle the load.