Truncates with large number of extents in a Locally Managed tablespace

I have a large table (70GB) with a very small uniform extent (64K) that I need to truncate. The problem is that index on the table has grown to 100GB as well. Now Oracle support wants us to truncate that table. The problem is that truncate table takes 12 hours to complete - Not too bad considering the number of extents the table and the index has. But being an uptime nut that I am, I wanted to see what can be done to reduce the time that it takes and so we went researching. I found one Oracle note that