need help installing harris bipod.
which harris bipod would be best ,and what mount,and how to mount
 for a G.I. stock.

GI brat had to send his rifle back to springfield to get a stud installed to mount the bipod.  He paid for the parts and springfield paid for the shipping as it was covered as a warranty repair.  The total was $45 out of his pocket for the mod.  you can see it and read about it here www.ar15.com/forums/topic.html?b=6&f=6&t=148

As for a bipod it depends how lonw to the ground you are.  Some people would go with the harris benchrest series as they allow the lowest profile to the ground.  I would go with the harris SLM.  Its the next size up and offers spring loaded legs, swiveling and a spot for a sling to be attached to it.