I suspect you could change your BIOS to run SATA in Legacy mode and you will find your drives will now appear as /dev/sdC0 and /dev/sdD0 though I cannot promise anything.
It is preferable to run SATA in native mode, and you could change back after installation though your fossil config, venti config, and plan9.ini would all need to be updated to reflect this change. I am currently installain onto a machine with drives in /dev/sdE0... but I am net booting the box from an old server and copying the disks from my old server. I am trying to say an install can be done but the install scripts may not be clever enough to cope. -Steve
