Confused- tapered head tube and BB size

Hi, just got my EMD 9 root beer XL frame (used) and am building it up.

Couple of things are bugging me, BB measures 68 mm wide but when I looked at the website, it says it is supposed to be 73mm?

How can I tell if it has a tapered head tube? It does feel like it has a very slight taper inside. Is there anyway to confirm? I can give the serial number stamped on the BB shell.

I never had a tapered head tube before, does it require special headset? Can a regular fork be used or does it have to be tapered fork?
Help please, I want to ride this thing!!!
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