If It's any piece of mind the GT's frame is so stiff you can pretty much jack up the whole car from one side. I've jacked my car up numerous times while being under the car. You can see that the side with out the jack starts to come up not to far behind the side with the jack. A true test to the frames stiffness I would doubt that you have incurred any major frame twisting or damage.
I would remove both rear belly pans and you will be able to see if they have been bent , twisted or cracked. Get the car up on a 4 post lift and inspect all other areas. ( belly pans, side splitters, wheel well liners etc.. )
I would say if there was any damage it would be to components that can be replaced so I wouldn't lose sleep over the potential of the frame being damaged
Also for the record I've been using a simple scissors type jack at each jack point and they work quite well !!