With a size 10.5 foot and a 6-0 frame...
With a size 10.5 foot and a 6-0 frame should I go with the 166 Heritage X or will I be good with the width of the standard 165 Heritage. Weight is 165 and mostly all sled access backcountry riding.
I wear a size 11 boot and am riding a regular width Heritage 158. I've never had any problems with toe drag on this or any other regular width board, so I don't think you need the Heritage-X. The only caveat I would add is that I do ride with a fairly wide stance (22.5 inches) and duck-footed angles (+15/-9) both of which help cut down on toe drag a bit. That said, I'll think you'll be fine on a regular Heritage.
If you are back country powder riding, nothing wrong with a little extra float that the Heritage X provides. Especially with size 11 feet.