Gas Tank HELP!

[75 Power Wagon]

When my dad installed the dual exhaust on my truck way back when.. he had to put a gas tank in the cab, and get rid of the original tank. Well, i dont want to have the tank behind my seat no longer, i want me some bass! But, I'm not exactly sure where im gonna put the tank now.. any suggestions to where to put the tank, and exactly who i should buy it from?

I had a friend recommend me to this site..
http://www.fuelsafe.biz/