I'm not sure about the 98 Custom e-grip, but I know for sure this'll work. http://www.tippmannparts.com/Tippmann-E-Grip-Alpha-Black-p/1627.htm
I would be surprised if the Tippmann 98 E-trigger didn't work, as the carver one has almost the exact same internals. However, this may be a case where you would want to play on the safe side.
Another thing to consider, do you have a feeder that can handle this speed? I recommend the cyclone If you don't, I love mine!