Congratulations!!!, You have a very good rear end, yes those are the mounts for the swaybar, and you are correct, the body mounts are the two holes per side under the "seat". That will make your installation a lot easier.
In post #7 you can see them in the pic. there are 2 factory holes in the body on each side with plastic plugs in the holes. All GT's have the rear holes, but none for the front sway bar, you have to drill them yourself. :yup: