Kitty Cat Snowmobiles

Anyone know the difference? The one I have was manufactured in 1972 so does that make it a '73? Any pictures I have seen all look the same between the two years.

thanks

The exact history is posted on here somewhere. It's a '72. The coles notes are that they made a bunch in '72 and sold them for a few years before making new ones again several years later. The 72's had a different motor than all the rest do.