No one makes a crossover knuckle for the 05-08 SDs.
Rize doesn't make their idler arm setup either.
Marty runs a dual hydraulic assist setup on his 08.
A skinny 40-41 should fit under a 10". Even a 40/15.50 may fit with the right wheel width, backspacing.
Afterall, I ran 40" Toyos on 20x10s under my truck which is only 9.25" over stock and the 08s have larger wheel well openings.
I've seen plenty of 37s under 4.5" lifts and even some 37s stuffed under a leveling kit of an 08....so I would think 40-41s should clear under a 10"