Nobody that I'm aware of currently makes (or made?!) for that matter a toilet with a 16" rough-in. Any toilet will fit on what you have, but there will be a space (maybe big) behind it to the wall. There are 10, 12, and 14" rough-ins. Your best choice to minimize the projection of the toilet into the room and minimize the space behind it, would be a 14" rough-in toilet. Keep in mind that most toilets designed for 14" are really one for 12" with a thicker tank to hide it; i.e., they often use the same bowl that projects forward from the toilet flange. The only one that actually adjusts the postion of the whole toilet is a Toto that utilizes the UniFit adapter. This takes the same toilet, and depending on the adapter you use, positions it so it will fit on either a 12, or 10 or 14" (the 12" is standard, the 10 and 14" adapters are an extra cost option). It keeps the front of the toilet at exactly the same place, not sticking out into the room more than necessary. And, no, you can't use this on any toilet, only those Totos specifically designed for it (and not all are).