Ive made it clear that Im not a mustang fan, but if you want a convertible mustang, then yah this appears to be a pretty good deal. Have you talked to them at all? Did they come down on the price? If thats just what its listed at then you need to get them to drop it more obviously.
Oh and the only major difference between the base and the gt .. you got it all wrong... the only major difference is the v8 ldo.
Make sure to post pics when you get it home.