Help!, anybody with a Riva red pipe!

I just bought a riva red pipe and planned on restoring it. Well after some reading I found that a lot of people are having problems with them getting a "small hole" plugged. Apparently there is a small hole in the pipe to allow water to enter. Problem is, When I pulled all 3 water fittings off the pipe, all 3 have EXTREME corrosion inside and I have no idea which one HAD the small hole. Also, What size was this hold because I'm going to have to drill it out.

Also, Is there anyway of removing the corrosion? Can I pour muratic acid into the water jackets?
 
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