Anderson Gun Shop in Yakima Washington did tang safety conversions on model 70's and advertized in the later 1940's in American Rifleman (I've seen ads from 1947). I have one but the tang is just behind the original receiver end and not large at all. I tried to take the action out of the stock a few years ago for pictures but the screws were tight and I didn't want to mess them up so I never got it out. I could send pictures but am not savy enough to post on the net.
Brad