Relocate gas tank

[Mownsno]

Guys I am wanting to relocate my gas tank from inside the cab to the rear of the truck between the frame rails. I know that this has probably been discussed but I hardly have enough time to enjoy all the info on here so I was hoping some of you guys could repost or help me with this project. I am looking to do this as easy as possible. I would like to get as big of a tank as possible but don't want it hanging down. Is there any kits for this? I have also seen a couple of pics where people made the rear marker lights in the bed a filler door to hide it instead of putting filler neck in bed of floor. Look forward to your input. Here is a pic of my truck. Its a 72 with a 68 clip.