Yikes!
I only have a older 1952 model 35 Remington and never took it completely apart. So I really can't help you.
Let's hope someone can.

 

You need to take apart your rifle to find out. Do you have barrel bands? How many? Just what version of 336 do you have?

 

A 1980’s vintage Marlin 336CS. It has the safety. It looks like the photograph below.

 

Either plug should work. Even when you have the max number of cartridges in the tube, the spring still has some give. For deer hunting, in my state of Wisconsin, a hunter may only have five cartridges loaded.
Andrew

 

I have a 336CS and it has the long screw version. The barrel is recessed for the screw. It's the only one out of 14 Marlins that has this???

 

Why do you think the 336CS is the only one having the long screw? Is there something different about the 336CS that creates the necessity for the long screw?

 

No idea. Everything is the same. Maybe they thought it would help to keep it retained better???

 

Long screw goes through both the plug and the tube. Should be a double holed tube end.

DEP

 

Why don’t you just sand the pits out and reblue it? No need to replace it

 

It is very heavily corroded. It would not look nice after bluing and the rifle is otherwise immaculate.