I never received your e-mail. Anyhow, no problem lifting the dually. But here is the tough question..... What tires do you plan on running under this lift? Being a dually you are limited on what you can do without relocating your rear springs, narrowing the rear axle, and resorting to custom built wheels all of which gets very expensive. If your truck was a SRW just about anything goes, but a dually is a whole different story. For this reason we generally stick to 37-38s with 8" lifts on these. But anything is possible.
FWIW, I plan on selling the entire drive train out from under my X (only 20" lift) soon. This includes springs, hangers, shocks, gusseted axles with 5.13 gears, drive shafts, crossover steering, wheels, tires, etc.. I'd make you a hell of a package deal.