Just to point out that you really, really, really! need to terminate the 4000 SCSI bus... if you don't the system will hang at boot.
There is a built-in terminator in the mouse/keyboard print at the back of the case. Maybe the SCSI ribbon cable came loose from that?
Try removing the drives from the SCSI cable and have it run from the motherboard to the terminator. If you then turn on the system you should be greeted with the famous kickstart 3.1 screen...
