spare tire is sooo ugly

[cst350]

Trying to get the spare tire tucked between the frame rails on my shortbed.

I was thinking that one of the old space savers (firebird, el camino etc. using a wheel adapter) that need inflation cans would work, but I cant find any information that tells me how big the diameter of these are when deflated and then inflated...

Also, don,t want to put the tire in the bed and have the gas tank behind the seat so those are not options. And the roads around here are littered with debri and potholes so flying "commando" is not an option.

Anyone know the sizes of those???