Use citric acid, that will take out anything stronger acids will.
Chances are, unless the core is badly corroded, your local radiator shop will be able to unsolder the tanks and "rod out" the core, then solder the tanks back on.
Make SURE they either seal or remove the oil cooler while doing this!!!! You don't want a slug of water or acid to get in the oil sump!
"modern" aluminum core rads become junk at this stage (everything past 1983 or so).
Peter
