If you want it to look "period correct," the scope must have a gloss finish. Matte finish scopes were not available until much later, probably some time in the '80s, as manufacturers sought to control costs, and matte finishes are less costly to apply (less preparation, etc.), and the "camo craze" for hunting was only then starting. All scopes on the market at the time any pre-64 was produced, and for many years thereafter, were gloss finish.

As to the sling, a leather military pattern sling would be appropriate, either a 1" or 1 1/4", depending on the capacity of your swivels. That was pretty much the primary sling available back then, and most serious shooters knew how to use the sling as a shooting aid, rather than only as a method of carrying the rifle. If you know how to use a military sling (or learn to), it will help a lot in accurate shooting.

Enjoy that old Model 70, a very fine weapon. I have one, made in 1948, sitting right next to my desk. I acquired it just a few days ago, and intend to disassemble it and give it a thorough cleaning this evening. I already removed the cheapy 3-9x32 scope some previous owner put on it, and will install a good scope either this evening or tomorrow. Of course, the rifle just looks so "right" with only its open sights. The caliber marking of ".30 GOVT 06" on the barrel is, of course, classic, as well. I couldn't believe it when I spotted that distinctive barrel profile in the used rifle rack at my favorite LGS, and they gave me a great deal on it, as well. I'm happy!

Oh yes, the scope bases and rings should also be gloss finished to be period correct (no matte back then for them, either).