That gas tank puts it into the late 60s.
The mix was that rich for the oils of the time, you can safely run 40:1 with modern oils.
There will be two lines. One carries fuel and has a pickup extension in the tank and the other is the excess fuel return line and attaches to the side of the carb body.
The ones showing the red removable tanks are probably left over 68's as Arctic Cats own sales literature shows the black permanant rear fuel tank.
I have a 69 Panther, Model P19SS, Serial No. 918689 that is about 200 miles from brand new (see pic below). My first sled was a 70 Panther, and that I bought new. The gas tanks on a 69 are in the back, 4 gallons. The 68's are the removable type, My friend from back then had a 68 that he bought new. The seat was available in pleated black standard or as an option with the Leopard pattern. You can clearly see this in the factory ad below. Not just black.
No, Bosscat is not wrong. You even proved it with your link. Did you look at the first pictures on the page you linked? They show the 246(P10H) with the all black seat and underhood red tank! YES, most 69s had the rear tank, EXCEPT for the P10H and P17J. Look at every model in the 69 line up and you will see every one has a rear tank except the P10H and P17J. Also, they started using leopard seat print in late 67. your black seat cover looks to be an Arctic Cat replacement that they offered in the 70s. but even those did not have the long flaps for the snaps like yours. Arctic most likely wouldn't have put a snap on the edge like that one has. Does that one have Cat head snaps?
ya see that now. No The seat on mine is not from this sled It's a remake of some sort. I had a 70 panther so I know what it's supposed to have. New seat is being made. It will be at least a sorta nice sled i guess. Not perfect in everyones opinion but ok.