For those automatic Owners, per the service manual here is the crank tool.
18355AA000 and 18334AA000 (one for the handle and spanner the other for the required pins.
The flex tool isn't specifically recommended for our FA20 AT6. I think the lack of an inspection cover makes it a non-possibility and the starter location makes it hard to lock anything reliably.
The "Cam" tool called out earlier MAY work but I think someone need to give us a thumbs up as the pin spread is very important. Also, given the cost of the SST this may be a much better solution!
Amazon: OTC 4754 Universal Pulley Holder
http://goo.gl/1kgEDB
Lastly, keep in mind that even after you get the stock pulley off you have to get the after market one on w/o maring the aluminum. Not sure how you all are accomplishing that for the AT6.