1964 Plymouth Valiant-Coolant Issue

I have cleaned out many rads with white vinegar and it works great. Lay the rad on the ground fill with white vinegar, it will take about 1 gal and let it set for a couple hours. Flush it out with garden hose, if there is still a bunch of calcium inside redo. If it has a bunch of holes you will find them. To neutralize use crystal draino,
get a gal of water and add some crystal draino. It will get hot but after it cools stir it around and fill rad, after a couple min drain and flush with hose, reinstall.