We haven't made the drive to Loring, but your idea of going through the Soo (not Sioux - it stands for Saulte Ste. Marie) -- it's a fine idea and will not only be a bunch more direct - but also have far less traffic than going the Chicago/Detroit route. At your abysmal 5mpg -- that'll be a big plus.
Entering Canada will be a medium deal -- as long as you have no drunk driving arrests on your record (at least ten years old). The Canadians are strict about that -- don't ask me how I know. Paperwork getting in won't be a big deal, I assume, although I've never had a race vehicle with me when crossing. As Jesse says, though, getting back into US might be more of a challenge. Again -- have lots of paperwork for everything. I don't know about hazardous/volatile fluids -- check first. And by all means -- carry a passport. That will ease your entry back into the States. We each keep ours valid and up to date. These days I just carry the wallet sized one -- but I think that's all I'd need in a situation like yours. But make sure everyone has one, even if they are not absolutely required. Terrorists and illegal aliens don't have passports nearly as much as they might have drivers license. Be prepared!
