I towed a 1000lbs double axle car-trailer with a 7000lb farm tracktor on it through the ups and downs here in Iceland a couple of years ago. I was as proud as hell of keeping up with traffic and generaly doing 80-90kmh with ease, even using 5th gear most of the time. On the way back home with the empty trailer it struck me, I had the 36x14.5.15's under it and the speedo was WAY off.
The lovely little 4D56 tows just about as much as your frame can handle. In a perfect world that would be infinity plus one <img src="/forums/images/graemlins/kewl.gif" alt="" />