I have solved the issue. In case anyone search next time, here is what I did.
Take out GTX780, use onboard to go into boot screen, select priority to boot using onboard.
Insert GTX780, but use onboard as HDMI out. Install driver.
Restart and change HDMI cable to GTX780.
For some reason, I cant load into UEFI bootscreen using GTX780 but onboard works fine.