How to downgrade to Stock Rom [HTC One X 3.20.401.1 CID HTC_203)
This guide is marked as "noob-friendly". Haven't tried it myself as I try to stay far away as I can from Sense:

http://forum.xda-developers.com/showthread.php?t=1859714

You were looking for 3.20.401.1? Here you can find the Nandroid Backups:

http://forum.xda-developers.com/showthread.php?t=1975140