FYI, my holding tank was missing when I purchased the boat
last year and I am in the process of reinstalling a new (poly) tank from Ronco Plastics (the original manufacturer) and a new marine
toilet to replace the existing porta-pottie.
For the toilet , I am looking at a Raritan
it will fit. These Catalinas came with Jabsco
toilets, which IMHO are basically a plastic bicycle pump with a bowl.
I plan a "Y-valve" between the toilet and holding tank to allow direct flushing
overboard via a thru-hull where permitted.
I also plan to install a 1-1/2" shutoff at the holding tank drain to isolate the tank from the pump-out hose and macerator. The valve will be closed in normal use, opened for dumping the tank then closed again. I will then flush the pump-out hose and macerator with fresh water via the deck
pump-out port. My intent is to keep the pump out hose clean to prevent bad odors and to wash away the human debris from the macerator so it does not corrode.
Raritan makes a macerator control
which monitors the macerator and shuts it down if running dry or locked up. A cool feature is that it will "spin" the macerator once-a-week to keep the cutting blades from corroding to the housing and seizing up. (a common failure mode for macerators.....)
I am also installing a larger diameter 3/4" vent hose for the holding tank (as compared to the original 1/2") to increase air flow to the holding tank.