I have a Pre-64 M70 in which the rear base has two holes, spaced .44" (11.2mm). Checking Weaver & Leupold they show the narrowest at 12.7mm. The base presently on the rifle has a quick-detachable ring, unknown brand, but is Weaver-style. I need to get a base extended so that I can move the scope forward.


Is there a source of any style ring that would have a base to fit the .44" spacing?

look at the older windage screw style Leupold or Redfield

Winchesters ha 2 maybe 3 different bases for the 70s , not counting post 64 . I'm going from memory but if you have weaver style and want more look for extension rings .
A bridge mount would use 3 screws originally . Extension rings are available for weaver and leupold , Burris , etc .