I see where you're coming from, been a while since I've had to align a truck with that suspension. Your idea sounds good, and should work. I would suggest that you start with getting the camber in where you want it first, which is easy to measure with an angle finder on the rotor face. Once that's set, you can shift the caster around by swapping the shims from the back to the front. Do the toe setting last, as the other dimensions will effect the toe reading.
Another option you could do would be to get an old style camber/caster gauge. Might be able to get one at a swap meet or shop equipment sale cheap, as most alignment shops do not use them much anymore. These mount to the hub once the dust cover is taken off, and can measure both camber and caster at the same time. It does take a little math work to determine the caster angle, but really isn't too hard to do. I will admit, it has been a while since I've used one, and the Hunter Hawkeye 800 has got me spoiled for doing it old school.
