I also did the tank strapped in the back, it did bring the suck. Lost a ton of cargo area and the fuel pump whine was extremely annoying. I would recommend a fuel cell set in the floor behind the rear seat to keep as much room inside as possible. I had a kilby skid, but it got old landing and dragging it over rocks. If you do stock tank in the bed, I would enclose it and insulate it for noise...? Fuel in roll cage FTW!
Personally I need my backseat again so I made a custom fuel tank that sits under the seat and drops through the floor between the control arms. Keeps cargo area and seat and doesn't hang down under the back.