I've now completed my purchase of the Gravis Ultrasound PnP, and the IPC SCSI RAID Disk Array Controller GDT6538RD 6x68pin, 4x50pin SCSI Adapter!
So this build now consists of the following components, many of which still have to arrive from various parts of the world, so it will take some time before I'm able to start with the assembly:
ASUS P/I-P65UP5 Baseboard with a C-P6ND CPU card

This fully modular 750W Power Supply

The Gravis Ultrasound PnP

the IPC SCSI RAID Disk Array Controller GDT6538RD

The Matrox Millennium II PCI VGA 8MB 2D card

This pair of Canopus Pure3D II Voodoo2's

And finally the CoolerMaster Cosmos C700M

Parts that I still need to buy are the following:
512MB of EDO RAM (4 x 128MB SIMMS)
2 x 15K RPM 68-pin SCSI drives with cables and terminators to match
A new in box Pentium Pro CPU to get its heatsink, fan and sticker (as I currently only have one of these Heatsinks and fans!)