Default S3 I9300 - United States - Help!!!?

So a local carrier here in Alaska decided to buy International phones for the purpose of reselling them. It looks like they go through a 3rd party to develop the firmwares and pump them out, a company called UltiMobile from Orlando Florida. I'd like to get this phone up and running, and the ultimate goal is to get it to work on AT&T's network. So here is what I've gather about this phone.

1.) Does NOT boot into an existing ROM, stuck at the Samsung screen.
2.) Able to boot into download mode just fine.
3.) ODIN does recognize it when plugging it in.
4.) Did not like trying to take a firmware via ODIN, failed with an error to read specific files (Line 1993)
5.) Firmware for this phone/carrier is not readily available if at all.

android4.0.4
baseband i9300uble6
Kernal 3.0.15-679767-user
se.infra@SEP-50#1
SMP PREEMPT WED JUN 6 15:43:48 kst
buikd #
ULTIMOBILE-SGS3-4.0.4-GCI-071112-3.0

The above information was taken from another post by an XDA member "AcerSnowman" who posted his phone that is also from this same carrier. Note the GCI in the name along with Ultimobile. I would assume that this information is close to the same, so hopefully it will help to find the proper firmware. At this point I'd imagine the best route is to find the stock firmware or a stock firmware that will work on this phone currently enough to get it up and running. Then I should be able to root it, install CWM/TWRP and worry about custom ROM and radio firmware? Does this sound correct?

Any assistance with this very specific phone would be worlds of help, thanks guys.