other than looks, the 450r looks pretty ugly. it would be a cool swap, but not worth all the time. to make the blaster good with the 450, you would need to spend some money on a great suspension setup.
Well despite most of everyones negative feed back ive decided to start the project, im going to upgrade the suspension on the blaster , ill start posting pics when i get started
The best thing to have when doing a project is something else to ride. The last thing you want to do is have two broken down quads and be in a rush to finish one to go riding. Keep the 450 as a daily rider. If you are looking for a project then start with a late 1970s or 80s bike engine. Parts are easy to find on ebay. I have worked with a lot of 1970s/80s yamaha street bikes so I made a short list of cheap motors that could work well:
SR250 Small 250CC single cylinder street bike.
XS400 Uses points ignition on 1979 and older.
XJ400 Full re-work of the xs400 motor. DOHC.
XS650 VERY TALL. You will see a lot of hill climb bikes with this motor.
XJ550 Very slim 4cylinder. See my profile.
I'm not a big fan of mixing brands when it comes to motors and frames.. but a swap I would like to try is a VF750F