my neighbor's 04 bone stock cobra(not a single mod) with about 1500 miles on it dyno'd at 351 to the ground around 70°F and about 40% humidity on a mustang dyno, although mustang dyno's usually read a tad low it hangs with other dyno's i'm finding around the net.
Here's a 2003 on a dynojet peak was 355.7 @ 6530 rpms
600lbs is a HELL of a lot of weight. that's about 6 tenths in the quarter and 2-3mph\
One has a full tank the other has 1/4? one driver weight 150 the other weighs 250, there's so many factors in street racing it's not even funny.