Fuel cell/gas tank help

Hey yall, i recently redid the trunk of my car, and added a new rear axle and all the new suspension parts with it. Unfortunately my gas tank no longer fits snug, it has to hit the suspension parts and the tire deck of the trunk to fit, and i dont like it one bit.

I was looking at fuel cells vs gas tanks, but i cant find a write up on how to install a fuel cell. Is it as easy as dropping it in and hooking it up to the existing gas line and fuel gauge sender?