this is what i can tell you from the pics. the gun started out as a field grade gun. and as you stated, someone had a simmons rib installed. from what i can see of the stock, it looks like a pre 50's skeet grade stock. the pistol grip cap on 60's guns should be all metal. yours looks like it has the winchester logo on it. you need to count the lines per inch on your pistol grip checking. early check was 20 lpi. 60's is like 18 lpi. if you were to take off the pad, and put a winchester period butt on it, the lop should be 14 1/4". what is it now with the pad? you need to make the forearm checking match the stock to be more correct.
the pad tells me the owner hunted with it, since winchesters never came stock with pads unless it was a trap gun. so function overruled perfection. if you desire to make the gun more original, the pad should be replaced with a galazans winchester retro pad. in 62 it switched from soild red to white lined winchester. and your serial number is smack dab in 1962.
