I wouldn’t put it on a 250. I helped put one on a 450 Yammy and what a guy doesn’t think about is the extras. Bigger stator to handle heaters and a rekluse clutch. It’s a big setup for sure.
When it comes to snow horsepower and torque are important. Riding a YZ-250 and 450 back to back the power difference wasn't that noticeable but the lack of torque made the 250 far harder to ride as it was weak when off the pipe. If 2 Stroke is your thing a 500 or built KTM is the only way to go.