have a look throught the net , theres force converters available that you just input the figures, then you may have to divide/multiply the time factor.

and yes your almost there with the break torque, its i.e just say we are talking 2wd, and the diff is set to a figure of 70ft/lb, if i lift one wheel off the floor, place the car in gear ( so the pinion cant turn) then apply a torque wrench to the hub nut, i should see 70ft/lb on the wrench setting before the wheel(hub nut) will turn, this is the pre-load of the diff.

does that help ?