You can wear out an LSD in as little as 25 miles running on pavement after swapping 235/75R15 spare in place of 31x10.5R15.
If you have tires different size than spare, you put the spare on the front, and the front on the back and the flat in the box. You really don't have to have larger tire as you will get the flat fixed and put it back where it came from, the tire from back to front and spare back under the truck. As you only every have one wheel off at a time, one jack is fine.
Note: if you have 2wd with lsd/locker and are running big rears/little fronts, you would have to swap both fronts to back, put back on front along with spare, a lot of work.
The spare is a temporary thing, you're not necessarily driving on it full time, which is why Ford could mounted spare on steel rim/use slightly different size as it wasn't to be there long and they saved a couple buck. You can get hitch mounted tire carriers and front mount hitch - puts tire up front counter balancing load e.g. camper in box.
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It can be PIA when box is full and flat is muddy, but them's the breaks.
Hence, why when my daughter had flat on back of her truck she called D. A. D. service as it was -25 and windy.