That would be a markII not IV . Finding one with a oriiginal composite stocked rifle might be hard to do.
maybe buy a stock off ebay like this- http://www.ebay.com/itm/Ruger-M77-M...462?pt=LH_DefaultDomain_0&hash=item460b6f650e
Then find a rifle in a later design to drop in it but heres some-
http://www.gunsamerica.com/902731674/Ruger+M77+Mark+II+7mm+Stainless.htm
http://www.armslist.com/posts/68670...a-rifles-for-sale--ruger-7mm-stainless--mint-
http://www.gunsamerica.com/96619770...77/Ruger_M77_MKII_7mm_Mag_Light_Stainless.htm
maybe buy a stock off ebay like this- http://www.ebay.com/itm/Ruger-M77-M...462?pt=LH_DefaultDomain_0&hash=item460b6f650e
Then find a rifle in a later design to drop in it but heres some-
http://www.gunsamerica.com/902731674/Ruger+M77+Mark+II+7mm+Stainless.htm
http://www.armslist.com/posts/68670...a-rifles-for-sale--ruger-7mm-stainless--mint-
http://www.gunsamerica.com/96619770...77/Ruger_M77_MKII_7mm_Mag_Light_Stainless.htm