1965 Safari tank, toilet, and flange help, please!

[65Safari65]

I'm posting this from a mobile device, so bear with me...

I have finally replaced the rear subfloor, and won my battle against the leaky fiberglass tank (interior epoxy coating, exterior seam fiberglass repair- not pretty, but effective).
What I'm wondering about now, is if anyone has any experience with mounting a Dometic 310 in the rear bath bench. Of course, I first have to do some fiberglass repair (previous owner cut the bench to fit the toilet...), but I'd like to get back to the hinged lid on the bench covering the toilet.

If so:

-How high up did you have to raise it, and what flange did you use?

-should I put something like plumber's putty on the flange threads when I install it?

Any help would be greatly appreciated.

On a side note, that's just water in the tank, for testing purposes. Two days without a drop!


Thanks!