If you happen to be from Spain, "Zinc" is pronounced "Thinc." 8)
From an article in Mustang Monthly: http://www.mustangmonthly.com/techarticles/mump_0907_zddp_zinc_additive_engine_oil/index.html This is the most concise explanation of how to at least rule out certain oils for our cars.
Mike's Tech articles have info on 3 oils with ZDDP: http://www.classicinlines.com/caminstall.asp
From an article in Mustang Monthly: http://www.mustangmonthly.com/techarticles/mump_0907_zddp_zinc_additive_engine_oil/index.html This is the most concise explanation of how to at least rule out certain oils for our cars.
The first thing you want to know about engine oil is if it has an "SM" rating, which indicates greatly reduced or zero zinc levels, which makes it harmful to your classic Mustang's engine. Do not use engine oil with the "SM" rating. Or, if you're going to use engine oil with the "SM" rating, use a zinc additive that will maintain proper ZDDP levels. Front and center for this issue is California, which wants all zinc eliminated from engine oil. Regardless of what government and industry mandate for engine oil, it is up to you to ensure sufficient zinc levels are maintained when you change or add oil.
Mike's Tech articles have info on 3 oils with ZDDP: http://www.classicinlines.com/caminstall.asp