the amount your wheels will be moved out will be the difference in thickness from the drum to the rotor. the drum is approximately .100, all you need to do is measure the thickness of the rotor hat and drum and subtract...
if your wheels/tires are close to the fenders, then you may possibly need a different backspace on your wheels... if you have 3/8" or more clearance you might be fine, but that could also be determined on how tight the suspension is... in regards to body roll etc...