yea as for a phazer being a 600 definitly not they were all 485 fan colled motors and they didnt go as well and the 440's did, the only 600 twin liquide cooled that i know of that yamaha made was the vmax 600 and the motors from them are a direct bolt in to a yamaha exciter 570 which is also a liquide cooled sled but as for putting a liquide in ss 440 your looking at a lote of work with cooling and motor mount because yamaha did not use motor plates they all hade different mounts off the motor
and if you need proof of the phazer being a 485 go to yamaha-motor.com, go to the sport section, then in the top right corner there is a spot that says hististory click on that, then on the left there is a spot to select what you want history on go to epic snowmobiles you will see, also yamaha has a online parts catalog with diagrams of all they stuff under that parts and service section up top of the page across from where the spot that says history is just to clear things up
but if you do swap a 600 twin in to a ss400 it will be one hell of a fast sled once its clutched and set up right