atlas shafts into english axle

hey guys im attempting to strengthen my rear end up abit, someone suggested using my atlas axle shafts with my english axle, when measured the atlas shafts are 665 long and the english 653 long, having a tranx LSD i believe the side gears are interchangable, and was thinking if i shortened the atlas's by roughly 10mm and changed the side gears this could be a very easy upgrade

atlas is on the left, english on the right
 
my question is how is the best way to shorten the atlas shafts?