If you want to use different parts of a gun and plan on painting it. I would go with the following parts.
Use the most of this gun
Cut of the back obviously, take off the scope and cut the finger guard and move it back closer to the handle. Lastly sanded down the very end of the barrel.
Then for the stock I would use some version of this gun.
There are several different color so thats why I said if you plan on painting it you could with a cheaper version. However both of those guns do come in black if you just wanted use the plastic as is.