Disclaimer: Do everything that is written the guide below at your own risk, I and the developer of this build will not take any responsibility for any damages over your device or experiencing data loss after applying this instructions to install Android Ice Cream 4.0.3 to your XOOM. Again, do it at your own risk.
What you need to do firstly are:
1. How To Unlock Motorola Xoom Bootloader.
2. Then root your Motorola XOOM to make a changes like making system level changes on your device.
3. Flash ClockwokMod recovery to your XOOM.
Once you've done with all the requirements, then let's port Android 4.0.3 Ice Cream to Motorola XOOM:
1: You need to download two files, firstly the Ice Cream Sandwich ROM .zip file, you can get it from this XDA-Developers forum and the second file is Google Apps for ICS, download from MediaFire. And then place all the files you have downloaded to the your tablet's root or sdcard.
2.And then open ROM Manager and tap Reboot into Recovery. This will make your tablet boot itself into the ClockworkMod (CWM) recovery, however sometimes it's not booting itself, thus if you experience that situation, then boot into CWM into a specific button combination.
3. From CWM, you must wipe data/factory reset, wipe cache as well as wipe dalvik cache.
4. After the necessary data are wiped, then it is time to flash the Ice Cream Sandwich to XOOM to install zip f sdcard -> select zip from sdcard -> to ROM that you've downloaded earlier.
5: The same steps like the above, install zip of sdcard > select zip from sdcard > to Google Apps file you downloaded earlier.
6. Once flashing process is finished. Now choose reboot system now.
7. Congratulation now you have installed Android 4.0.4 Ice Cream Sandwich to your Motorola XOOM.