With you being auto, I wouldn't think for a second about throwing a higher stall converter in your GT.
On average, a better converter drops 3-5 tenths in the 1/4 mile.
Next step would be long tubes. I'd cut your current mid-pipe and have it welded back up to fit the new long tubes, it's what I did on my Notch.
Also, you'd be surprised how much weight you'd shave off with a set of big-n-littles on your car if you are going for 1/4 times.
I've seen in several apps where the skinny fronts are good for a tenth in the 1/4. I've also seen two fold improvements by going to a full boot, inner-tubed and screwed ET Drags has made a huge improvement at the track.
Of course, LS-7 heads, cam and full exhaust on the Batmobile and you'd be left scratching your head.