I did one of those many years ago on a fairly large program. I don't remember exactly how I went about it, but I created symbols for everything and then saved the program without the addressing, as symbols only (library file maybe?...can't remember exactly...).
Then, using db ascii export/import, I was able to assign those symbols all new addresses in the PLC5. Then when I copied and pasted the logic, the addressing was already done.
That would be a waste of time on a small program but it's worthwhile on a large one.
You'll need to search and replace your OSR instructions with ONS.
There are a handful of other instructions that either work differently or are incompatible...Maybe Ron B. will help out with more details on that...