Clean the sling with saddle soap and treat it with neatsfoot oil or mink oil or dubbin. The ATI stock is not a significant improvement over the wood stock. Take that off it you want, steam out any dents as much as is easy, soak it in linseed oil, hand-rub the linseed oil to finish and put it back.
An original magazine will show up eventually, pay $50 if you are in a hurry and money comes easy, be patient and you may find one for $30, typical is $40. A gunsmith on the west coast, Bits of Pieces, sells 5 and 10 round magazines manufactured new in S.Africa by K-Mag. Get a front sight blade as others have said, they aren't expensive and the rear sight on these is quite good, I wouldn't sacrifice it to facilitate a scope mount. A Weaver TO-1 mount is less than $20 new and needs a gunsmith to drill and tap three holes. It uses tip-off rings which is less than ideal, but they work. Unless you use sight through rings, which raises the scope higher (and the Enfield No.4 will have the scope fairly high anyway), the iron sights will be obscured, but they won't be hurting anything and they'll be nice to have if something goes wrong with the scope in the field - just detach the scope with rings, and carry on hunting. Maybe look for a Beartooth comb-raising kit if you find the scope a bit high.
It did have a sight guard on it originally, and if you want one it can still be installed. The bit of barrel that was chopped off was around an inch and included the bayonet lugs. I think that's why some people did this - they thought the bayonet lugs were ugly. Machining the charger bridge and rear sight mount off is an expensive way to make the gun uglier and less useful.
If the bore is good, a magazine and a front sight blade is the minimum and you will have a useful hunting rifle.