Picture looks like it's stock in back (no weight, no seats?) but possibly torqued a little on the TB in front, probably to compensate for the sliders. So you're likely stock. Nice looking ride though!
I'd probably drive it for at least a day before putting 35's on it.. will be faster up the passes. plus I think there's more to it to run 315's than just a twist of the torsion bar, at least if you plan to flex it out a lot.