I'm wondering what the difference is between Standard and Long life antifreeze is chemically. I have read that the Long Life's corrosion inhibitors are is a hybrid between conventional and the Dex-cool kind, and is better for use with Aluminum engines. Would long life (non-Dex-cool) coolant cause any issues with Cast Iron engines? Or would it be better to use the traditional antifreeze that you need to change every 30k miles?

you can use the modern long life coolants in old cars if you flush all the old stuff out. It's just a better coolant that lasts longer