.22/77 synthetic???? Why don't you have a look on the Ruger website.
It's the calibre of the shooter that counts not the calibre of the rifle.
Ruger 77/22 All Weather.
As for the value depends if someone wants one. £50-£75 ????
Ruger 77/22 Magium Boat Paddle Stock..
These stocks are also known as Skeleton stocks.