For ICS 4.0.3 ROM's you will need the newest firmware located here
. Be very careful please! You can find all types of the firmware on the second post of this thread
. On that second post there is different carrier versions, what ever carrier you are pick the 3.24 version of it.
Once you have the newest firmware, you should still be able to flash older ROM's, but these ICS ROM's are amazing.
The ICS ROM I am using is: CM9 by TripNRaver