I'm about 99% sure that those are not cracks......but years ago I was breaking trail.......it was getting one hell of a work out with those plastic paddles lol.......then BOOM.......secondary exploded.......it look like a bomb went off on that side of the sled......belley pan,hood,didnt even look like it had a belt guard, beat up the primary clutch too......that was all fixable, but I did have a chunk that went through my snow pant into my leg that the Doc had to pull out! so with that all said just be careful.......I guess alum you can not have magnafluxed because its not magnetic......I had some connecting rods x-rayed at a place that builds Airplane engines......now they might use untrasound instead!
They all look like that.