You need a new forend with picatinny rail mounts for you to mount your grip on. ATI makes some as well as other manufacturers
GOFFA Council Member
Gun Owners For a Free America
"Today, we need a nation of Minutemen, citizens who are not only prepared to take arms, but citizens who regard the preservation of freedom as the basic purpose of their daily life and who are willing to consciously work and sacrifice for that freedom."
~John F. Kennedy