Have you put the original
3.0 ROMs back in to check if the motherboard is still working: ROM 391523-01 (bottom/socket U6B) and ROM 391524-01 (top/socket U6A).
Be careful as the ROMs are shorter than the actual ROM socket so they should be put in correctly with the space at the left hand side looking front-on to the motherboard
The
Kickstart 3.1 ROMs should have 391774-01 in the top socket (U6B) and 391773-01 in the bottom socket (U6A) with the space on the left looking once again straight on to the motherboard.