its called starting from fucking scratch. Look at my post. Look at the partition layout. Make your partitions look like mine, except sized accordingly. Its not that hard.

Install MorphOS first. Boot up MorphOS and look at it. Looks nice, right? Ok, boot from Debian.

Use Guided in Debian and select "largest free space" or something like that.

Once that was done and installed, MorphOS no longer booted as expected. Then edit yaboot.conf, update it while in Debian as previously posted in this thread. Then you're all set.