Gorilla Glue will expand to fill spaces, but that glue in those spaces will NOT be strong in a structural sense! Gorilla Glue is basically reformulated expanding foam insulation. It is a moisture cure glue, so misting the wood with water first is a good idea as it will draw the adhesive into the pores of the wood. Polyurethane glue is good if you have two mated pieces that contact each other well. Epoxy is better to fill a gap and have it be strong in some sort of respect. This knowledge comes from experience building many custom doors for clients in Boston, as opposed to reading crap on the internet. Just so you know! Also, the polyurethane glue will scrape off like popcorn when expanded and dry on the outside of the joint. It also cleans up really quick with lacquer thinner. Another note: Epoxy will not stick to wood that has been waxed with Butchers Wax, so if you wax your stock first making sure no wax gets inside the crack, any epoxy that oozes out will break right off the wood when cured!
I hope this helps. Oh, Wenig Custom Gunstocks makes nice stocks and they will fit them to your action or provide them semi-inletted and unfinished for ya in a number of stock styles. Google them up and have them send you their catalog. I have used them before, one was a Savage M110L that was about 50yrs old. Small amount of inletting, then slapped her right together! Father in law was very happy, as it was his first deer rifle and he had hacked the stock off when he bought it at 11yrs.