Let's put it this way.So you think the 4 flat is legit?
There was a reason the best bang for your buck mod you could make on the 99-04 Mustang GT was gears for the 1/4 mile and 0-60 times.
I think conditions will prove that it'll be somewhere in that territory. A jump in gearing from 3.73 to 4.56 is completely reasonable to knock a half second to 60 though. 315's don't add much rotational weight.