Buy a 97 Arles. It's the most sensible answer from where you stand now. you have an ST already so just swap all the bits with your ST and repaint only the tailgates and hard top. Sell yours as a pretty unique artifact in and of itself as a black SW.
There were quite a few 97 Arles SWs for sale here about 9 months ago... I was chomping at the bit.
When you dismantle both, take great care to clean up the ST roll cage bits, seat belt mechanisms, etc.
When you are ready to leave the Defender game X years from now call me. I'm licking your 97 Arles ST Auto with AC now! Make sure to transfer over the Boston Acoustics bits as well!
------ Follow up post added October 9th, 2011 12:13 AM ------
oh yes and I have just the top for you as well.