Watercraft engine swap

W/C

Lots of money. First off that isn't the sled to do it too. You want a GenII or even better a Edge. You should be able to find one with a long track already on it.
Water craft motors are NOT just a matter of changing a couple of parts. Crank has to have a end put on it for a clutch. Case has to machined for a snowmobile ignition. You will need to buy an adapter for the ignition side also to be able to run a 650 or storm style waterpump. You will need ultra or XCR magneto, flywheel, CDI etc. Also pull starter. Next 3 cylinders and a head to cover them. Water manifold as well. Also carbs and a clutch. On and on.
PSI1200 builds that stuff and does a fantastic job but it's going to be expensive.
Take some time and read through the Water Craft thread and you will start to understand.

Further discouragement: The motor you're looking at is basically what the old 750 Storm motors were. Those weren't great performers even in their own time, but compared to modern motors they are "duds". If you really felt you had to do this, just go buy a Storm motor and forget about trying to convert the PWC motor. If you're wondering about why people convert PWC motors, do take a look at the thread mentioned. It will explain a lot about what is going on with the conversions and why what you're thinking of doesn't make the most sense.