That sounds like a steep learning curve! I got there in the end, here's the detail in case it's helpful to anyone else down the line.
The basic problem is that the hardware detection finds the SCSI adaptor even if it's disabled in BIOS. If it is disabled, then everything hangs at detection. On installation there are two lots of detection - one is at the very beginning where driver modules are loaded. Usually this is only a network card driver, but if there's a SCSI adaptor that gets included too. Consequently, if the adaptor is disabled the installation hangs, and if it's active, the SCSI driver gets installed there. The hwconf and modules.conf files seem to work with Kudzu on the second hardware detect, when the boot process has progressed into the graphics phase, and don't affect the drivers loaded in the first detection.
My fix - active the SCSI adaptor and use the 'noprobe' option on install, manually loading the network card driver. In due course Kudzu finds the SCSI adaptor on the 'new hardware' search. Edit modules.conf to remove the SCSI adaptor line, delete hwconf and run Kudzu manually. When it finds the SCSI adaptor, hit the 'ignore' option, then reboot and disable the SCSI adaptor in BIOS.