I am looking at one made in 1958 and was wondering????

If you are referring to whether or not the pre-64's are drilled and tapped, the short answer is yes for your 1958 model.

Pre-War Model 70's were drilled and tapped on the receiver ring only. Some scope mounts (Stith, e.g.) got around this by using the holes drilled and tapped for the receiver sight to mount the rear base.

Post war Model 70's are drilled and tapped on the receiver ring and bridge. The hole spacing on the bridge varies, since target models and magnum actions had part of the bridge machined away to accomodate a clip slot or the longer magnum cartridges.

Thanks for the answers.OB