Ruling out it's a 03+cobra then it shouldnt be much of a race. I dont think a stg 4 would do much good against a properly drive 03 cobra on the street..but who am I?
As for CAI and Pullies....decent mods on a gt but nothing great. Gears are the down side to many 4.6's as they like to live a little higher in the rev range. If those are his only mods then you will have him no doubt. Most "bolt on" gt's will not leave the low 15 high 14 range with out them getting the crap ran out of them. As for the 05's....I lost interest in stangs about 2 years ago and havent really kept up...but I would guess it's would be closer.