Dashes are usually designed to work with the exact bike theyre on....
The first problem is that the engine in the 400 is different, and has a different redline, and so the tach would not function correctly I'd say.
The latest model 300 and older ones have a different dash appearance though, and they are likely interchangeable. I have the older style, and I do like the look of the newer style, but IMO it's not worth the trouble of changing.
Also, I believe instrument clusters are quite expensive, especially since you cannot reset the miles on a used dash. Then it would just read wrong all the time, a loss for you and any future owners IMO.
I would leave it if I was you, but if you really want to tear up the front end, would be a rad project to see.