I had a thought I was mulling over. I have a bunch of nice leather slings with the "uncle mike" type of hardware. I also have a handful of pre 64 model 70s with the standard 1" sling swivels. So obviously they won't work together.

I wondered if the uncle mike studs would be the same size and thread as the factory swivels? Or are the stud-swivels on the pre 64 super grades the same size as the standard grade swivels?

My thought was that if I could replace the factory swivels without damaging the gun or making the holes larger, I'd switch them out and save them in case i sell the guns.

I think murray custom leather makes a wide sling that narrows to 1”. I have one of their 1” and it is nice but want to get one of the others. I need to drive up there they are not far from me.

I have a couple of Pre 64s. I just cut the sling loop off of the stud, redrilled the stud and used an Uncle Mikes detachable swivel.

Hip

Alteration of the sling studs and swivels is not the answer. Hurts the value and ruins the rifle, IMHO.
There are good standard leather 1 in slings available-military style-that with keeper adjustment that help a solid shooting position while hunting.
None of my model 70 pre-war rifles would be subject to those alterations or the sub-standard slings.

Pre 64 Model 70 Winchesters are rifles----Not shrines!

Hip

I wasn't going to cut anything off. I just wanted to temporarily replace with a stud and keep the original sling swivel. I just didn't want to strip out the hole either. Not a huge deal. I can find some 1" slings if need be.

As suggested above, "tapered" rifle slings are available in considerably greater width than the associated "bases". In terms of "affecting originality", first question whether the specimen is yet original & relatively pristine. If not, non-issue! Believe too, aftermarket pre '64 Model 70 repro sling bases are available as proximate copy... to have one's way with as preserving originals. The separate as 'last shoe' question, whether the sling configuration binding barrel to stock and beyond, is of such feature-condemned consequence in accuracy impinging concern.

I have my small cluster of collector pre '64 specimens and my "user friendly" field several. Common '06 chambered Standard Models showing field wear & tear. I'd replace those swivels if convenience/ergonomic comfort concerns. Just not to "F" with a yet original stock often defined as "recoil pad installation, as terminal modification!

Just some considerations and alternatives reflecting...
My take!
Best!
John