1)

I assume you have HFS partition on both drives for boot images and also MorphOS system partitions on both too. You should keep both system partitions bootable (flag in HDConfig), but edit the bootinfo.txt file on the HFS partition to match the system partition device name on that HD. And remember to run "HFSSetMacBoot Boot:bootinfo.txt" command in the shell after every edit of the bootinfo.txt file!

For example, if you have DH0 (HFS partition) and DH1 (SFS partition) on the disk 1:
- Add BD=DH1 to the boot-script line of DH0:bootinfo.txt
- Run in the shell: HFSSetMacBoot DH0:bootinfo.txt

And if you have another HD partitioned for example like DH5 (HFS partition) and DH6 (SFS partition):
- Add BD=DH6 to the boot-script line of DH5:bootinfo.txt
- Run in the shell: HFSSetMacBoot DH5:bootinfo.txt

I think that should do the job and then you can boot either of the HD from the Alt key bootmenu. Unless there is some bug on using several HDs somewhere...

If you want to make it even cooler, you can edit the small butterfly gfx in the bootinfo.txt file to contain something to recognize which partition it is ;) I've added numbers there on the empty space :) But remember the HFSSetMacBoot again!


2)

If you don't want to have two HFS partitions, you might be able to select the boot device from MorphOS's early startup menu. But you have to boot the system with BM option for boot.img or press lmb or F1 keys when booting. You have to be sure that both installations are the same version then.


3)

And third option which comes in my mind, is to create a boot menu with Bootcreator program, then you can have just one HFS partition, but you get into the menu always which can be annoying too.