The easiest way would be to set your new IDE as a slave, boot into Linux, create a Linux partition (Ext2, Ext3, etc) on the IDE, mount it, copy the contents of
/boot to the new partition, and then install lilo in the MBR of the IDE.
You will have to make modifications in your
/etc/fstab and perhaps in
lilo.conf.
Don't forget to create a Boot Disk, just in case.
And test everything before erasing the first SCSI drive.
I believe I covered everything.
