I'm guessing that you want the drive bootable and lilo to write to the MBR on that drive, therefore it would be most convenient to have that drive as /dev/hda...
Will the drive(s) on the Promise controller be the only drive? Then you could just disable the on-board IDE controller in your BIOS.
If you will have other drives on your on-board controller, you could use the following to get the Drive on the Promise controller enumerted first. You will need kernel support for this:
CONFIG_BLK_DEV_OFFBOARD=y
Then you can pass the "ide=reverse" option to the kernel when you boot (kernel > 2.4.x) or "pci=reverse" for 2.2.x kernels.
FOr example you have a boot labeled 'linux' in lilo.conf, so at the lilo boot prompt
Code:
boot: linux ide=reverse
This tells linux to enumerate the ide devices from last to first, so that the Promise controller will be IDE0/IDE1.