No offense!
Just start pulling some pieces.
Looking back, I would pull rave valves on any "project" I might buy.
Would know if rust was there, or just a seized piston.
From what I have been reading, replace pump cone oil, clean raves and carbs, check that when riding that oil is going down out of the oil tank, even might run premix the first tankful to make sure that oil pump is working.
Just a few maintenance issues that get over looked on a lot of skis.
JD