Brian,
I have seen several pole buildings that were high enough to store full size motor homes in.
Another suggestion on the heating, have one side of your building facing East. Check out the Mother Earth passive solar heat article. It is much easier to add while the building is being built. I am thinking seriously about adding passive solar heat to my shop. The thing that gave me the idea was the roll-up door I have on my pole barn that points East, it is painted dark brown and in the middle of Winter if the sun is shinning the inside of the door is so hot I can't touch it.
The passive solar heat will not be my primary heat source but will cut my heating bill considerably.
David