Dulude Wood Stove info/help

A buddy of mine just gave me a Dulude wood stove. Google hasn't turned up much. I was wondering if anyone knew anything about them. I'm putting it in my barn on a concrete floor. I'm mainly wondering what size chimney would be appropriate. I'm guessing 8" but right now on the back of the stove is what looks like an 8" to 6" reducer. I'll double check this tomorrow. Looks like galvanized and not stove pipe. It was hooked up to a stone chimney that had no chimney liner. I'm planning on going up through the ceiling and using class A chimney. My friend doesn't know anything about it, it was in his house when he moved in. He heated his whole house with it last winter so I figure it will be great for my barn. Thanks for the help.

Dave