Is this a Rupp

#7
Fox with an Arctic Cat tank looks like... You'll have to get the numbers off the motor to see what it is to get parts etc. Look on the top (may need to scrap some paint / crap to read it). The next question is "restore" it or rebuild it to ride. Doubt if anyone would consider it ultra rare, so I'd rebuild & ride it! "Rare" or not? These guys on here can tell you without a doubt.
 
#10
I don't think that's the wrong motor, looks right to me. The tank does look like a Arctic cat though, here is what the Fox rounded tank looks like.

 
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