I pulled the original toilet (Groco K) on Crazy Fish a few times to rebuild it while cruising, replaced it with a Lavac and replaced the Lavac with an electric unit with a macerator at the based of the toilet.
I installed a bronze screw in circular access port on the vertical surface in front of the shelf that that the toilet mounts too. Pacific Seacraft installed a similiar one to provide access to the fuel gauge mounted directly on the fuel tank. I can just fit my hand thru the port to attach nuts to the bolts and hold a wrench on the nut.
Another approach that will provide better access is to remove the drawer cabinet under the main berth. You will be able to see and access the lag bolts or whatever was used to mount the toilet.
Quite a bit of unused space back behind that cabinet. I built a shelf aft of the cabinet and mounted an electronic compass for WH autopilot a number of years ago. A couple of days ago I installed a Newmar semi water tight box and terminated the new wires recently installed in the mast and the wires running from the electrical panel as well as a NMEA 2000 tee to link the new B&G Triton mast head wind indicator and the Depth/Speed/Temp sensor to the cable that runs back to the Nav station. The teak bungs that cover the screws for the cabinet were replaced once. I find I pull the cabinet frequently enough to not install the bungs.
Crazy Fish - Maintaining, Upgrading and Sailing a Crealock 37