Okay. So you have two original 30s. 30m (master) and 30s (slave). You also have a new 80.

Try this:
Remove all drives.
Install the 80.
Install and run the builder.
Install 2.0b13 (or whatever final version you want)
Verify the 80 by syncing 1 file to it.

If that works:
Install your original 30m as the slave. You will need to change the jumper.
Boot - you will see database errors.
Go to shell.
cd /drive1/fids
ls
You should either see lots of files (pre-fidsift) or a bunch of _directories (post-fidsift)
If you have files (pre-fidsift):
cp /drive1/fids/* /drive0/fids
If you have directories (post-fidsift):
cp -R /drive1/fids/* /drive0/fids
shutdown
Remove 30m and install 30s, being careful about the jumper
Reboot
Resync / rebuild databases & test.

If all went well, your 80 is now master, your original 30s is the slave drive, you should have (nominally) 110GB capacity and all of your files should be there. You also have your old 30m sitting on your desk, for whatever use you choose.

EDIT: Also, be aware of a potential builder bug that has popped up from time to time.