Here's the available Android 2.3.6 Gingerbread stock ROMs available for AT&T Samsung Infuse 4G. Some of these stock ROMs were leaks and under beta test for development but these are original and unmodified firmware versions.
Stock ROM I997UCKK3 [Android 2.3.6] 21.11.2011
Stock ROM I997UCKK2 [Android 2.3.6] 09.11.2011
Stock ROM I997UCKK1 [Android 2.3.6] 09.11.2011
Stock ROM I997UCKJ4 [Android 2.3.6] 28.10.2011
Stock ROM I997UCKJ2 [Android 2.3.6]14.10.2011
Odin Guide for Flashing the Stock ROMs
1) Install Kies on your PC just to ensure that the drivers for the Infuse 4G are already installed
2) Download and unzip the stock ROM files packaged
3) Use and run Odin3 v1.7.exe
4) Set the Infuse 4G into download mode - turn it off or pull battery then in-place it back again ,
( Just press and hold both Volume Buttons while plugging in the USB cable cord)
5) In Odin, the COM: Port box will display that your phone is already connected
If there is multiple files in the packaged you may just put the desired files on each designated slots.
6) Click the PDA button and choose the PDA_.tar.md5
7) Click the PHONE button and choose MODEM_.tar.md5
Bootloader for APBOOT_.tar.md5 and CSC file for CSC slots.
8) Press Start
9) Once it finishes, it will reboot to recovery. Just select "delete all user data" and then select reboot system now.
Heres the stock rooted version, deodexed with busybox and SU and Zipalligned installed. The installation is simple - just download the Zip, Boot into recovery, wipe data and dalvik cache then flash and reboot.
Stock I997UCKK3 Rooted, Deodexed, Busybox, Zipaligned, 2.3.6
Stock I997UCKJ4 Rooted, Deodexed, Busybox, 2.3.6
Stock I997UCKJ2 Rooted, Deodexed, Busybox, 2.3.6
Stock I997UCKK1 Rooted, Deodexed, Busybox, ZipAligned 2.3.6
Everything you wanted to know how to do some tweaks on your Samsung Infuse 4G like unlocking, rooting, reverting back to original stock, unbricking, kernels, modems and custom ROMs. Just visit this super thread of prasadudwadia at XDA-developer.