How tall are the drives? I think the SCSI Powerbooks can take up to a 12mm drive - if these are 9mm drives, would it be feasible to make up an adapter PCB (or even a ribbon cable) that mounts under the drive? The drive could go in backwards, connecting to the PCB at the far end, and then the PCB mounting a socket for the motherboard ribbon at the "back" end. The PCB could have SMT termination resistors onboard, and connect points and/or a regulator IC for extra power.
Making an adapter would allow easy replacement of the SAS drive without needing to perform the mod on every one. The same board with a 2.5"-3.5" SCSI adapter could be used in a desktop Mac.