AT&T GS3 Odin Files topic

Im trying to odin my phone back to stock because I want to sell it. Ive tried many times using the latest odin version and the android 4.0.4 file. I read somewhere about something like the bootloader being on 4.3 or higher while the software is still on 4.0 and that is a reason why it is not booting past the glowing samsung logo.

Anyways im just looking for a file that contains The Bootloader and PDA file to go into Odin

Thank You