Hardware Wizard asked for IRQ5, DMA3 and address 02B8, all of which I set. Windows 98 Hardware Manager reported no conflicts for these settings, but stated the card was not working and put a yellow "!" on the card icon.
The Troubleshooting Wizard says that the NI-488.2 software is verified OK, the GPIB hardware is verified OK but the interface fails the sequential test.
I've just had some confirmation from NI tech support that the GPIB-PCII card only recognises NI-488.1 and so is totally non-compatible with the modern software which only works with NI-488.2 compatible hardware.
I think I'm pretty much at the end of the road with this card.