I'm going to go from 40 to 42. RCV's are the biggest must, the knuckles are a great to have as well a the ball joints. You'll be just fine axle-wise with those mods and going to a 40/42 but will def need that extra inch of lift.
EVO makes a relocation bracket to the left lower corner using OEM bolt holes. I'm sure it ould also work on the right side as it mounts to the hinge point.
Still on the tailgate but at least its not front and center by the handle.
EDIT: sorry, see someone beat me to it
You'll be fine, I ran those same spec wheels on my narrow's both before and after wheel spacers. I had tereflex 4.5" short arm kit, artec truss and RPM steering bars; super similar to yours. I went to Windrock with that setup before replacing my front axle.
Your rear axle shafts will leak before the front snaps lol. Both of mine did; i should have done chromoly at the time but as each side went out, I replaced individually.
Eventually, I did RCV front shafts, artec full front truss with c gussets, lockers and dif covers... just to get smacked by...
You can run 40's on bone stock axles; all you need is a lift, gears and maybe spacers depending on the wheels and backspacing. I went with 5.13 gears.
I wheeled on stock axles and 40's and never broke anything; its just taking time and being careful. I started taking more trips so I beefed up...