Looks like you can pick up a front/rear sway bar from a GT500 for about $150 shipped on ebay nowadays. Think that's a worthwhile deal compared to spending $3-$400 minimum on aftermarket bars? I think the GT500 bars are what they added to the track pack '10s

 

I got my Eibach sway bars for right around $300

 

I'm in the market as well, but I dont know if they'll fit an '05 GT.