Adam Swift to fullback for me.
Reasons being.
Half back combos are built. We need to let Lomax and Gaskell to continue their eduction together. Swapping and changing halves upsets the balance and momentum of a side. All great sides have settled half backs.
Makinson needs to continue his development on the wing. I dont think he provides a long term solution to replacing Wello at fullback. Rationale being that fullback is one of the four key creative positions on the field, the others being the hooker and the two halves. Therefore you need someone with good footballing skills to play there. Swift being an halfback/fullback by trade has these skills. Makinson has only shown an ability to run reasonably quickly in a straight line, and finish in the corners. He hasnt shown a particular talent for being able to read a game well.
Makinson and Turner need to continue together to help build their understanding on the pitch.
Putting Gardner and Turner together would degrade the pace significantly on that threequarter line as Turner would need to slow down on a break to allow Gardner the opportunity to catch up. Thereby negating the advantage Turners pace gives us. Similarly opposition wingers know that Gardner cant score from any distance, this means they can double team on Turner, and take the risk that if Turner gets the ball to Gardner that one of the second rowers would be able to cover back and tackle him.