It'd be easier and less expensive to re-barrel. There's a bit over half an inch difference in the case lengths alone. There likely isn't enough chamber area length to just re-chamber. The WSM is 3 thou larger at the cases head too. That's definitely no big deal. However, you'd be going from a belted case to a non-belted.
Think in terms of machining costs of around $100 plus per hour. Plus, if your smithy doesn't have the reamers, you get to pay for them and you don't get to keep them.
Rebarreling starts at $150 plus the cost of the barrel.(Epp's)
You'd need a spacer in the mag well too, but that's easy enough.
Whatever you do, find a local source for the WSM brass or ammo first.