Sprint LG LS720 (Optimus F3) owners who wish to unbrick or unroot their devices can grab this “LS720ZV5” Stock Rom From Below link:
Download Firmware Available: LS720ZV5_00.S5_00.P25013.cab
To save the LS720ZV5 ROM, please right click the above link and select “save as” or save target link as”.
Please notes that this ROM is used for Sprint LG LS720 (LG Optimus F3) Only
It comes in .CAB format instead of KDZ. You may need some tools to convert it to .kdz or file so that you can use the KDZ update tools to flash the ROM onto your LG LS720 (Optimus F3) device.
Or You can try these: