Yes, the mustang will be improved, but the improvement is a bit cosmetic, an addition of about 50 ponies and likely an independent rear suspension. The Camaro will still spank the Mustang. Don't get me wrong, I'll test drive a new one so I have something to compare the Camaro to, but it's not gonna' be as cool as the Camaro, I can tell you right now! The GTO vs. Mustang, however will be a close match up (LS1 of course). The GTO weighs in @ 3725, while the Mustang is a little lighter @ 3560. The GTO has 350 horses and the mustang, 300. The GTO has 365 tq. and the Mustang has 320. The power to weight ratio for the GTO is 10.642 lbs per single horse power, and the Mustang is 11.866. One would think the GTO will likely overtake the Mustang with the spare 1.224 lbs of power/weight, but only in the 0-100 mph race. 0-60, the GTO comes in at 5.3 seconds, the Mustang at 4.9. The GTO comes in at 12.9 sec. in the 0-100mph race, and the Mustang at 13.2. The 1/4 mile, the GTO comes in at 13.8 seconds and the Mustang at 13.5 seconds. Pretty much neck and neck. Go to this sight for the specs on both.
http://ford.jbcarpages.com/Mustang/2005/index4.php
http://pontiac.jbcarpages.com/GTO/2004/index4.php