well i don't know about the rest of you guys but i always use a bimetallic union when i install my freeze plugs.
a alum rad doesn't touch the engine it's seperated by the rubber hoses. i think if you keep the cooling system in proper shape and change your antifreeze and only use distilled or di water you won't have that much a problem. no ions to conduct current, i guess. i have heard of this ruining parts even on newer vehicles if they cooling fluid was let go to pot.
