Well, hold on, just slapping in a set of the inward facing seats is a tad misleading. There are a number of things you need to make sure you do aside from simply bolting them in. The biggest concern is the seat belt support that runs under the tub. The seats themselves are just bolted through the thin skin but the seatbelts are attached to cross-members and frame points, not just through the skin.
Some threads you should read regarding the safety and install of these seats:
http://www.d-90.com/forum/showthread.php?t=9562
http://www.d-90.com/forum/showthread.php?t=9523
http://www.d-90.com/forum/showthread.php?t=1723
