I just pulled my under-bed spare carrier off this weekend. the last thing I want to do if I have a flat is to crawl under the truck to get the spare. I don't know how old the spare is but it's all dry rotted anyway. I have another spare to use and I'm going to mount it up on the side of the bed between the tailgate and the driver side wheel well. I looked at a couple of mounts that are for sale
(like this) but I think I'm going to fab my own. (have a design in my head but haven't tried to build it yet)
I can take a pic of the pieces tonight when I get home if you need it.