I think that a 2014 is what you are looking for, it spines about 55 pounds. Unfortunately the 2014 is only currently available in the X7 model from Easton. You may be able to find some old stock though.
The Platinum shafts are available in a 2013 which I believe is right around a 53 pound spine. The 2013 may work well as is or perhaps you can trim them down a touch shorter than your Bear arrows which would effectively stiffen them a little.
Lancaster Archery is listing 2013's in both Platinum and xx75 Camo Hunters as being available.
Good luck.