If I were you I think I'd try to find a good, competent gunsmith in your area and tell him exactly what you want. There are several custom barrel makers out there that he could order a new barrel from. I would think that there has to be a barrel maker out there that could duplicate the original contour, so that no stock work would be necessary.

The pre-64 model 70 is a special rifle, I own one myself. Let a competentgunsmith do thisthing right for you.