What type of anti-freeze should I use on my 1953 international pickup truck with a stock radiator?
Regular ethylene glycol was the antifreeze used then as now. The corrosion inhibitors , and other additives have changed and vary from brand to brand , but basically the same stuff. In '53 there were a few still using methanol/alcohol , but it was a high risk of fire. Modern corrosion inhibitors focus on aluminum but should work on your copper and brass radiator and cast iron engine.