Ford trucks also used have the gas tank behind the seat inside the cab. My friend's truck was cobbled together with a couple different model years, so he had two tanks with individual fillers in the bed and the third in his cab.
Another issue with the side by sides is the exhaust is right under the cargo area. If your spare gas tanks leak, you have a combustion source just waiting for that gasoline.
GM also had the gasoline tanks mounted outboard of the frame rails (side saddle tanks) causing them to leak if you were hit broadside. I never heard of a remediation for that design but know there were some high dollar law suits due to it.
