I have to admit that I'm not much of a snowmobiler (not a lot of snow in Southern California), but from what I understand the modern crop of high powered 4-stroke snowmobiles are completely insane. For less than $10k new you can pickup an Arctic Cat M1100 turbo that produces 177 horsepower and will catapult you into the nearest tree/rock/Sasquatch faster than you can say BOND, JAMES BOND. However, there was a more civilized time when Snowmobiles were slower, but probably even less safe. Find this 1970 Rupp 440 WT offered here on eBay for $500 buy-it-now or make-offer.
According to OldRupps.com the Magnum was one of Rupps early snowmobiles with production starting in 1970, and the 440 version was available in standard and wide (as seen here) track. The 440 cc 2-stroke is good for something around 40 horsepower.
See a better way to get around in the snow? firstname.lastname@example.org