The high MPH usually comes from lack of traction at the starting line.
Most cars I've seen run, including my previous SRT-4 had higher mph when the 60 ft wasn't good.
Whenever I did get it to hook up better at the line, the mph went down and so did the 1/4 time.

An example...
My modded SRT-4 ran 12.7 @ 118 mph w/bad 2.2 60 ft times on street tires,
with practice I got it to run 12.5 @ 116 mph w/ 2.0 60 ft times.
My buddies 71' Roadrunner runs 12.2 @ 110 mph w/1.7 60 ft times on drag radials.

Either way, 113 mph is kind of hard to believe from a stock SRT-6 no matter what the 60 ft time is.