I thought this thread was just hilarious about the decisions to be made on selecting a replacement toilet.  So I included almost the whole thread.
You will be interested to see what Kelvin selected at the end of the article

I now have a second GMC and need to do this again so I also wanted to follow the decision process.
Here are my feelings

I replaced a Tetford Aqua Magic, because the flat valve would never seal. The Tetford ceramic ball valve is a new design and I wanted a
proven design, with out cables so I got the Sealand.

I used the Sealand 510 ceramic about $300. Was recommended by Jerry Work in several seminars and has proven to be very good.
this one has a ceramic bowl and a ball valve, no cables, and has a better record than the Tetford.
had to rotate the base plate gene

Pulled the toilet out of my '73 last night. Pretty straightforward job.
I had a leak. The bowl wouldn't hold water for long and I'm pretty sure part of the leak was ABOVE the sliding seal.
First question: Will a standard beeswax seal work to seal this old AquaMagic to the floor? That's not what was in there... but knowing my PO he just might have been more creative than necessary.kelvin

Yeah... I looked into it a bit further this evening. Turns out the local RV Parts place has the real McCoy hanging on the wall. A foam rubber ring, indeed.
And while I was there I looked at the Aqua Magic Bravura toilets. $207. A tank of fuel. It's sure a lot nicer than the old Galaxy - which will start spitting out broken parts soon, I'm sure.
The only possible problem I see is the size of the Bravura between the mounting ring and the back wall. Going to test fit the old toilet and see if I have a spare inch of room back there. The Bravura is longer than the Galaxy that came out.

Not looking real promising. The Bravura is significantly wider and longer. Wider matters, too, for cleaning around it.
I think the Style II might be a better option. Don't care for the "side lever" flush pedal, but it might be in the way less than a front-mounted pedal. It's only a 3/16" wider than the Galaxy and maybe 1/2" longer. China vs Plastic, too.

It would mean replacing the flange on the floor, however. Bolt pattern is different than the old Galaxy. The Bravura is a direct replacement. My flange is cracked and distorted, however. Wise to replace it while I'm in there anyway.kelvin

I'm not tying to say anything against Eugene's seal toilet, but budget was an issue for me. I know there's six ways to do one thing on a gmc, and if budget wasn't an issue i would defer to Mr. Fisher. I'm just posting for those who need every penny they have so they can fix MORE stuff on their coach.peter

Yeah, that's sort of where I am. Wasn't planning on replacing the toilet so a $50 job has turned into a $200 job. I can't let it become a $300+ job. There's fuel to be purchased this summer, after all...

camping world has the thetford aqua magic style II that i just installed for $176 (member price), i went with the high profile model. It's a china bowl with the foot pedal on the side, which for us was a huge improvement over the hand lever at the back of the toilet. It also has the ball design over the flat valve. It also has a full size seat, so i can go anywhere to get a new seat if i need to. peter

So what is involved in replacing that flange? Is the flange itself a standard RV part? Mine is sealed to the floor of the shower with some pretty sticky stuff. I assume any good sealant (and not and "adhesive" ) would work there.
Does the flange just slip into the black tank or is it screwed in some way? Haven't had much luck finding info on that. The Maintenance Manual says remove 6 screws and "unscrew". Going to be tricky to unscrew with that sealant holding it to the floor... but...

I just removed the toilet flange from mine to drop the tank. The sealant between the floor and the flange isn't a problem it will unscrew easily. The problem is the 8 rusty screws. I had to use an hand operated impact driver to loosen the screws enough so I could turn them out with a screwdriver.roy

> Fellers: Phooey on this china stuff. Just go buy you the 140 buck replacement at rv world<>
> less than two hour replacement job, that is if you are small enough to get in to where you can get line loose in rear. (We will just not discuss how I know that can be a problem. OK? OK!). jofarr,

I am guessing that it is CFOs that most need a china bowl, eh?

It takes a special kind of nut ^W socket to get the terlit out, as I recall a deep socket, 1/2" "loose nuts"hardie

Yep, it's the CEO who wants a china toilet.
could be she is the one who has to clean the toilet?

I like the quote " I don't use it much " from an earlier post , spoken like a true Guy, we don't leave the seats up either!

The flat slide valves never cleaned well and the seal never lasted, that is why the new Tetfords are now ball valves, and the Landsea
always were ball valves gene

I just removed the toilet flange from mine to drop the tank. The sealant between the floor and the flange isn't a problem it will unscrew easily.

Yeah... not on mine.It's entirely possible the PO was in there before me. There was gooey rubber sealant everywhere - basically welding the downpipe to the floor of the coach AND the shower stall. Finally had to cut the top off the flange and get in there with various tools to remove as much rubbery stuff as I could and a pair of vice-grips to get the remnants out. 2hrs and much sweat was expended. Now I just need to figure out what I need to put it all back together.
The problem is the 8 rusty screws. I had to use an hand operated impact driver to loosen the screws enough so I could turn them out with a screwdriver. kelvin

I don't think the screws were OEM. There were three different kinds and there were also a couple T-Nuts in the shower floor - or something. Like I said... one of the DPOs had been in there mangling it.
"What the hell - I won't have to work on it in the future. It'll be some other poor slob's problem." kelvin

I am not sure what made the final decision, but the result was a Seland 210, and here is how Kelvin did it.  Young guy that does great work !