This is a neat project, CW and I appreciate that you've shared the fun. Great too that Roxanne watches over you as you pull your project together.
A couple pics make me wonder if that bare patch on the left side of the receiver isn't part of some previous work filling in scope base screw holes. I may not be seeing it right, but I can almost make out three spots in a row which are slightly different in surface appearances than the rest of the receiver. If I'm wrong, I need to get my eyes checked. If I'm right, someone did a nice job of it.
It's been a long time since I handled one of these, so I don't know if what I think I might see is even in the correct position radially on the receiver. Twenty-some years ago, I sourced a new 222 magazine and a scope mount for a friend with a 340 and my dad D/T'd the receiver for it. I only handled it enough to admire my dad's work and return the piece to my friend, who went on to wipe out many woodchucks on his dad's farm thereafter.