The only hard part about converting is getting the revision numbers correct. Because of the differences in RCS/SCCS revision numbering, there can’t be a 1:1 mapping.
We punt in the following way: sort the revisions by date and check them in in that order. That way, the revisions will probably be numbered the same but may not be on bushy RCS files.
In order to convert, I need a rev/parent rev/date tuple. I sort on date and then check them in oldest to newest.
For RCS, I can get 2/3’s of what I want from rlog; I have to parse the RCS file to get the rest.
For SCCS, I can get the parent/child relationship from sids, and the rest from prs.