Hi Hugh,
Don't know if you also check the Rennlist forum but there is a good thread going right now on AC's. Someone sited this link:
http://www.griffiths.com/porsche/ac/911ac/index.htm#Condensers
There's a lot of good Porsche AC info on there and the project ice they did is pretty amazing but I'm sure it's high dollar. Let us know what you come up with. The AC in my 88 coupe has been out so long I forget I have it!
Mark