well you don't really specify the block device perse, but rather whatever you set the jumpers on the device reflects what device it will be...so since you ask a question of the such, i assume you don't quite understand fully what it all means so i'll break it down
primary master = hda
primary slave = hdb
secondary master = hdc
secondary slave = hdd
so since your saying your cdrom was hdc, then that means you had it on the secondary IDE cable set as a master drive...
so if you want it to be hdc, then you will set it as a master on the secondary cable, and if you want it to be slave then you will set the jumper on the device as slave on the secondary cable, and so on...
as of can you put both cdroms in the machine at once, then the answer is yes and no...also, i will explain..
the answer would be yes if you have an opening on one of your cables to put another drive/cdrom
and obviously the answer is no if you don't have any more openings...
as of emulation, yes both can have scsi emulation, that will be taken care of the append line that you will add to your lilo.conf or grub.conf file, depending on your bootloader...a typical addition to one of these files would be :: append = "hdc=ide-scsi" or if you get both devices connected then it would be append = "hdc=ide-scsi hdd=ide-scsi"
also make note that you will replace where i have hdc and hdd to the proper devices if they are not what they are on your machine.