Dear Stu C,
I did the following, I took the base for a Lyman 48 for a Mauser 98 and put it on a post 64 Model 70 there was a very good fit(want me to post a picture?), contourwise. So I think the converse would work, that a Lyman 48 for a Winchester would fit a Mauser. The only problem that could very well exist is that the position of the screw hole would force the sight to interfere with the bolt.
As far as G&H scope mounts are concerned, I can't speak for every base and mount but there is an amount of mirror symmetry. Within reason, I believe that you could rework a right-handed base and mount for an 03 Springfield or small ring Mauser to work for a left-handed large ring Mauser.