Those motors have a stage II Whipple kit on them.
Stock, the rev limiter is at 5400 rpm.
This kit consists of a re-programed PCM, which raises the rev-limiter, and alters timing and boost controls. It also consists of a water re-route to the innercooler, and a smaller pulley.
A Merc 700sci in this state of tune produces aproximately 820hp +/-
Dustin has done a really fine job of producing horsepower upgrade kits for the 600sci/700sci motors.
I love my 600sci Stage II.
Hope this helps,