Pics of the drives you wish to setup might help, clarify what is there and what needs to be done
Another thing, if the previous owner had an external scsi cd-rom, he might have removed the internal scsi-terminators from the motherboard. Stick a 25pin scsi terminator on the external port to end that part of the scsi chain.
Might help, might not.. helpfull lot aren't we? :-)
Really, some scsi setups need black magic or voodoo to get working correctly.. lol