The IBM 9114-275 (IBM Intellistation POWER 275) is equipped with SCSI Ultra320 SCA80 disks but you needs IBM F22870 hdd trays to install them.
CRUX PPC is targeted to experienced users thus the installation process it's not so trivial... It works quite good on pseries machines.
CRUX PPC provides Fluxbox as standard window manager but you can easily install Openbox and others ones using CRUX (main project
To have a real nice desktop experience on those workstations you need AIX from IBM.