As far as I know the 350 seats won't fit the 450s and vice versa.
of course, with some modification, there are items that will fit, that normally wouldn't. Now, the CB & CL seats will swap out, as long as you stay within the basic models (like CB & CL 450) but you have to watch out for particular years. The early 450s (don't remember exact years right off) were hinged at the rear and won't work with the later models like yours.
Later on, Bill