Find a pump that matches the output of the stock pump. Mount it as close to the cell as possible, most pumps that I have dealt with are pushers, not pullers. Myself I would modify (cut a hole) in the cell and adapt the stock pump to it.
i buiolt my own fuel cell and cut the hole to fit factory pump/ sending unit
this, with a ford tank or similar up between the rails in the rear would be good to
