Numrich sells a replacement forend tip for the Model 63 made of plastic for $10 and change. Part#23.
Supposed to be in stock. The steel ones are OOS.
63. WIN Accessories | Numrich Gun Parts
I don't know if Numrichs plastic F/E cap is a modern re-make of the Winchester plastic part.
Winchester did use a few plastic forend tips on the M63 for a while. They're difficult to tell from the blued steel ones by simply looking at them.
Original steel ones are difficult to find.
I'll look and see if I might have one left around.
The op-rod and cap have to be assembled. Then that assembly is installed onto the rifle with the op-rod spring in place.
You have to compress the op-rod spring up into the op-rod and hold it there.
There's a tiny hole in the side wall of the rod up close to the cap (as an assembly).
Push the spring down into the op-rod from the breech end with a pencil or other suitable dowel. Then you have to catch the end of it and hold it in the compressed with a small punch or even a nail works well thru that hole in the side wall.
Then slide the cap & rod and it's compressed spring inside of it and the pin hanging out from the side down onto the forend.
You have to line up the hollow end of the op rod to slide over the end of the recoil spring screw head that's down in the forend.
That recoil spring screw is just a stub of a headless screw but will slide up into the op rod.
When you feel them engage & slide together,,pull the pin from the side of the rod holding back the op rod spring and at the same time push the cap w/rod down the rest of the way into position.
Hold the cap in position as the spring will want to push it right back off again and you'll have to do this all over.
While it's in position, replace the forend cap screws on each side of the cap.
When fitting a new cap,,dry run and fit the cap first to make sure the screw holes line up. Quite often they don't. You can adjust the bbl hanger a little for some movement,,reverse it altogether for some more. Once in a while the wood needs to be trimmed a bit to set the cap back to allow the screw holes allainment.
Take your time.
If you need an extra cap screw or two, Weaver type scope mt screws work ,,or any 6-48 really. Just round the head to pretty them up.