Follow up on original post
Just to follow up on my original post here, I did return the rebuild kit for the old WC Headmate pump and buy the Raritan PHC-LBA. The job turned out to be about what I expected with a few twists along the way but all-in-all a quite do-able DIY project. At the risk of stating the obvious I thought a brief walk-through of the process I went through to replace things might be helpful for anyone contemplating doing this job.
It was a great opportunity to completely disassemble everything and get the bowl and seat parts of the head, as well as the raised area that it sits on sparkling clean and looking like new. Before disconnecting the old sanitation hose, I pumped some detergent and clean water through it. Immediately upon disconnecting the hose I fitted a small plastic bag held in place with a rubber band over the hose to contain any odors - worked great. I filled the holes where the old assembly was with epoxy to prevent any spilled water from seeping in. Placement of the new pump assembly is important. Be sure to allow clearance to attach the hose that supplies water from the pump to the bowl. Also in my case I had to be careful to make sure I didn't position the unit too close to the doorway or the door would hit the bowl and not close. Sounds obvious but dry fitting of the bowl will help you avoid these problems. If possible you'll want to reuse any holes where the supply and outlet hoses pass through. This is where I had the most difficulty. I had to drill a new hole (1.25") through a cabinet so the supply hose would be positioned near the front of the unit. The intake on the old unit was in the back and the supply hose could not be routed in a way to keep it from kinking. As it was, even moving the hole I needed to add a 90 degree elbow to attach the supply hose to the pump intake to keep the hose from kinking. (Building up the platform that the head sits on would have solved this problem in another way.) I was ultimately able to use the existing hole for routing the outlet hose but had to carefully position the unit since the large sanitation hose can't make a sharp turn in the restricted area I was working in. The most perplexing issue came up after I had everything assembled. (At this pont I'll say when you test the unit use a cup of water rather than a bucket full.) I put a cup of water into the bowl and pumped away, promptly seeing the cup of water end up on the floor via some unknown path. A more careful repeat of the test revealed that the leak was where the outlet elbow bolts onto the pump housing. I checked the bolts for tightness and they were cranked down tight. I checked the hose clamp on the sanitation hose thinking water might be leaking there and running down onto the fitting making it SEEM like the bolted on connection was leaking. But all that appeared ok. It almost seemed like a gasket of some kind was needed. The cause of the leak was the joker valve not being PERFECTLY aligned. It was shifted just slightly to one side which prevented the connection from sealing properly but still allowed me to assemble everything so it appeared correct. The rubber valve is so flexible that part of it can easily get compressed into the outlet hole which caused the leak. Now all is well and working properly. I did have to purchase a few things besides the PHC-LBA: New supply and sanitation hoses, extra supply hose and a vented loop (and mounting screws) to fit on the supply line between the pump and the bowl, a 90 degree fitting for the intake hose to the pump, a 1.25" drill bit, some hose clamps, small expoxy repair kit, carriage bolts and washers to attach the PHC-LBA to the floor, and a box of latex gloves.