If you do go the spare route, I beleive that you need to be careful of the size. I don't think that a posi rear deals well with different size tires for very long. Help me on this one folks!
I go the AAA and cell phone route. I think that some of that stuff you put in the tire in case of a puncture would be a good idea. After that some fix-a-flat, plug kit, portable compresser would be nice. But then you may also need a jack and wrench. No room left for favorite drink!
Rick