It is a good thing that you guys are out here keeping me on my toes.
Yes, the M-42 mount registration distance is about 2mm longer than the Minolta SR mount, and it is about 1 mm longer than the Minolta AF mount. The M-42 lenses will go onto a Minolta. This is something that I am really happy to know, because there are some M-42 lenses here that can go onto something other than just my Vivitar 450/SLD camera body. Guys, there are a lot of Minolta SR mount bodies around here, and I do have those adapters. Thanks.
Also, in actually going back into the boxes and finding the literature for the Minolta Camera Company Limited manufactured threaded lens mount adapters for the Pentax and the Leica lenses, yes, the Pentax version does work. The Leica adapter instruction sheet is the one that says that they cannot focus to infinity when a Leica lens is screwed into the adapter.
Well, for a 40 year old memory on this subject, it looks like I was only half right.
Latte Land, Washington