Well Ed, if you come through Sault Ste. Marie, you'll end up going through the U.P. of Michigan, nothern Wisconsin, upper Minn and N.D. And your right, all thats up there, for the most part are forests.
I personally wouldnt worry about breaking down in the U.P. and needing help. In all my years traveling up there, from one end of the U.P. to the other, all Ive ever found are great people, who will go out of their way to help you.
If you go that way, you'll probably drive M 28 through Michigan. I dont remember the speed limit 60, maybe 65, but theres hardly any police up there and you can haul some ass, watch out for the deer though, their all over the U.P. and northern Wi.
Personally, I would much rather break down up there than driving the southern route.
I also wouldnt go the same way I came. Your only young once so have an adventure.
I cant help you with any info on Minn or N.D. Ive only been through the northern parts of those states once.
let us know which way your going so we can give the police a heads up