Get a new one
If your looking for more power, i suggest you seriously look into a different sled, pipes are fine but then you have to clutch it ne ways, the best thing i would think of is a clutch kit, but i know here in canada they run around 200-300$. Once you start putting parts on a sled that size you might as well as bought a larger displacement. I've also looked into pipes and i've noticed people sayin on a really small sled, a fan cooled one anyways, they can reduce performance. Some things i would do with your 440 is look into UFO's for the roundslide carbs, i hear they work quite well and if your sled has them reeds are good too. The only pipe i would put on would maybe be an exhaust can, and make sure if you do anything you set your clutching up correctly and watch your plugs, keep em more rich rather than more lean, you'll have less chance of getting into trouble, there might be soome performance left on the table but its better than rebuilding your entire engine. hope i helped.