With reference to your question, download the original firmware of KU5900 here:
http://csmg.lgmobile.com:9002/swdata...00/V10P_00.kdz
then follow the steps found here:
http://xdaforums.com/showpost.php?p=24164378&postcount=23
After a successful flash, you can upgrade/flash and root to a stock P970. Follow below.
This is what I did, grab/download all the files on this thread:
http://xdaforums.com/showpost.php?p=23790405&postcount=171
- Follow steps #1 up to 9.
- It is important
DO NOT EXECUTE OR PERFORM STEP #10 Choose CP file or you will flash your radio and will have no signal problem with loss of IMEI.
In short, skip step #10.
- And take this
IMPORTANT NOTE, in step #11 in Choose AP file, do not select the .FLS file, instead select the .BIN file.
- Proceed with step #12 to 16.
Just follow the steps I wrote above and you'll have a fully working KU5900 with GB v20b. Just upgrade/flash a newer version (v20o perhaps) after you successfully flash/root.
Enjoy!