You could probably modify just about any track system to any snowcat and make it work, with enough time and money. To take BR350(?) tracks and modify them for a SV 200 would be a matter of making sure the tire guides are the same width to start with. If they are not then it is probably not a worth while modification. Then is the track/sprocket pitch the same, i.e. the center to center measurement from grouser to grouser? If not then you will need to build new belting to match the pitch to the SV 200 and to the bolt pattern of the BR350 grousers. The width difference is easily modified by cutting or realigning the grousers and if you need new belts any how should be no problem.
Did you find a good deal on some old tracks?