Which toilet fits?

[SilverHoot]

Want to purchase a new toilet for my 1967 Tradewind rear bath , I believe any Airstream with rear bath were pretty similar. So the question is which toilet will fit. Mine did not have a toilet installed when purchased and the rear of my trailer is completely torn apart to replace the floor so I cannot measure the area where the toilet will go. I am going with the original bath layout. Like to hear which toilet others have used.

Thanks, Michael