If I wanted to switch my three position Model 70 safety for one coming from a lefty Model 70, can it be done easily? Is there a lefty model out there that would like a "wrong side" safety who wants to swap?

If I understand correctly, you're wanting to put a left hand safety on a right hand gun? Putting aside the question of why, you're looking at a lot of trouble. I won't say that it wouldn't work because someone is liable to go to a lot of work to prove that it's possible. And it would be a LOT of work.