D14 head core plug replacement ?'s

I posted awhile back on a D14 that I thought had a cracked head. Some suggested checking the core/freeeze plugs for leaking and low and behold they were! Thanks everyone! I was told I could use standard automotive freeze plugs. I measured and they are an inch plug. I called my local napa store and asked if they had any. They said they had brass and steel and had three different depths depending on how thick your block/casting is. My stock plugs are steel. Should I stick with steel or go brass? Also, what depth? I would imagine the deeper the plug, the better the seal? Let me know what you think and your experiences with them.

Thanks for your reply.  I guess your right about the steel ones lasting 50 years. lol  My core plugs actually aren't that rusty. In fact, they don't have much rust on them at least on the side I can see. They seem to be leaking around the edges. As far as removing them, I've had good luck with the method you described on auto engines so I'll give it a try on these. If I get time, I'll post pictures of before, during and after replacement. As far as the depth goes, I guess I just need to pull one to see how thick the casting is.