An interesting thread similar to this one from long ago can be found here:
http://www.chiefdelphi.com/forums/sh...?t=20055&pp=30
From what I've read, it sounds like 47 for 1998 and a tossup between 25 and 47 again for 2000. A better opinion would likely be given by someone who was actually around back then though, all I have is what I could scrounge up on CD as I've only been around FRC since 2007.
Edit: found a photo of 47 from 2000.
http://www.chiefdelphi.com/media/photos/12954 They are the pioneers of the swerve, first making on in (if my research is correct) 1998.