I'm having the same issues right now. I have, to this point, combined both forums into one new forum (downloading the old forum folders, changing to the new folder's forum number, manually moving the forum folders into the new server, then updating the index and stat files). That part was actually a lot easier than I had expected.
Right now, I am trying to combine site registration folders. My issue is that there are about 250 of our combined 2000 registered users that overlap. We have taken the memberslist.cgi and the emailfile.cgi and imported them into Access, combined the files, merged both forums membership lists, sorted them by e-mail addresses, then purged the later registered duplicate username. At this point, my next step is to export them back out into the cgi files, but I, too, am having difficulty finding a script to do this without massive amounts of labor. I don't want to make people have to re-register, but it looks as if I may have to enter all of the data by hand into the user's cgi files.
Has anyone else figured out a work-around for this?
I'm getting close to desperate, too.
-doug