Doughnut behind the seat (rear mount tank)

[chevy72blu]

Anyone running a large rear mount fuel tank figure out a spare tire mount? I just had a lightbulb: build a mount for a small doughnut behind the bench seat in the cab. I cant imagine a fullsize spare fitting behind the seat, but then again I have never seen a 5x5 doughnut, either. The idea would be to limp the truck up to 50 miles to have the damaged tire repaired.

I want to eventually take the truck on long road trips; driving around town isnt much of a concern. I am running a Boyd's custom 20 gal EFI cell. It mounts high and takes up a great deal of space.

Knowing you guys, I figure there must be some trick ideas.