I am getting a 20 kw electric furnace for my cabin... I think it says to use 240 60 amp braker... I may have 220... that OK? I do have 200 amp service... anyway... 6/3 wg or 8/3 wg?I think the book says 49 amp draw... dont have book now... tks

No, you have 240v. We all do. 120/240v to be more precise.

If the book says to use a 60A breaker then use either 6/2 or 6/3 depending on if the unit requires a neutral or not.