Replacing toilet... flange question

I doubt it.
You may take real close look at the flange. Some are simply screwed on to pipe. You could take it loose, apply some thread compound and then screw it back in until correct elevation is made. It would have been good to do this prior to putting down the sub floor. Some are a slip fit into the tank if it is straight down.
Flange should be screwed down as that is the only way RV toilets are secured to rig.

Odd floor flange...

I would say yes, you will need a spacer. There are several types available at your local hardware store, Lowe’s, Home Depot, and plumbing supply. Brand names like Sioux Chief, Oatey, Genova. If you’re in doubt, I’d go to a plumbing supply house with pictures and get their advice.

:):)

Good catch, Chris!
Closer look it appears to be a residential floor flange as there is no holes for RV toilet.

Don't do what I did! I put in new flooring had my new gasket sitting on the sink cabinet, and got the toilet reinstalled. Beautful job! I got up off my knees and noticed the new gasket still sitting on the counter. AARRGG! It went in easier the second time.
Jesseannie

There are about as many flange/mounting systems for RV toilets as there are toilets. Some are compatible with numerous models and some are not. Check the installation instructions on your new toilet and see exactly what is required.