700xx

You would need to build a new chassis. The sprocket alignment is easy one to solve .The biggest problem is swingarm pivot point. I know a way of doing it ,or should I say, I have seen some pics on the internet that made it simplier to do.
The stock 450r chassis would break ,even at the thought of this motor being fitted.

Also a stock 450r rollin chassis and 700xx motor will weigh 430lbs . The 700xx motor and chassis can be made to match that weight.