Dixon, who helped the Old Parish reach the semi finals of the Principality Cup in the regular season, takes over from Dragons' Aled Thomas who replaces Craig Evans at full back whilst Bridgend's Nicky Griffiths make way at scrum half for Ospreys' Martin Roberts.
Assistant Coach Rees said, "James brings something different to this side. He is a little unpredictable and maybe that is what we need against a side who will play it only one way. I am looking forward to seeing him play and to seeing the other new faces too."
Elsewhere behind the scrum, Tom Cheeseman moves into the centre from the wing to replace Dai Flanagan who has a slight shoulder problem, whilst Bridgend's Roger Davies and Pontypridd's Chris Clayton are named on the wings. At forward, Craig Mitchell takes over from the injured Phil Osbourne on the tight head and Will Jones replaces Chris Dicomedis at lock.
Ed Shervington continues at hooker despite being sent off against the French - the tournament organisers felt his second yellow card was sufficient punishment.
"The changes are in no way a reflection on those boys who played in the week, I want to stress that," said Davey. "We have three games remaining and we need to utilise our full squad."
Tuesday's heavy loss to the hosts has left Wales in no doubt about what they have to achieve tomorrow. If they win with a bonus point they could sneak into the semi finals - if they lose to a Pumas side who are ranked fifth in the competition and who defeated Ireland in Cournon on Tuesday, they will be left to battle it out for one of the middle or lower places in the competition.
Davey said, "We have looked at them and we have picked accordingly. We don't want to become involved in a forward battle because they have proved in this competition already that they enjoy that kind of confrontation.
"Our plan will be to be competitive on their ball and to make sure we take the game wide and run their big forwards about."
The conditions here in the Auvergne region of France are such that the squad have been losing significant amounts of body fluid during the games. However, fitness coach David Watts and his staff have done a wonderful job in keeping the players suitably hydrated as yet, there have been no problems.
"We have to take off our hats to the support staff. It has been very warm out here and keeping the boys hydrated and fit has, perhaps, been the toughest job. David Watts and his team have been fantastic," said Rees.
Wales: A Thomas; C Clayton, T Cheeseman, D Hewitt (capt), R Davies; J Dixon, M Roberts; R Gill, E Shervington, C Mitchell, W Jones, D Day, C Everett, R Shellard, A Powell
Replacements: D George, R Cornock, J Connors, C Dicomedis, R McCusker, D Lockyer, N Griffiths