Check out
http://docs.sun.com/source/816-7326-20/ch06_fc_controllers.html#72403.
Just for interests sake why go back to 327R when you can go forward to 415F. 327R had all sorts of really nasty problems. As our systems are covered under Platinum support, we arranged (about two months ago) for Sun to upgrade all our 3510's to 413 and they refused to do it and said wait for 415 as it fixed all the new problems associated with 413.
Did you try to upgrade to 413 and it went horribly wrong or are you wanting to revert to get better performance?
Stephen