Your question is messing me up.
Your Miyata takes an English BB. Is that the (-E) referance?
The frame is 68mm wide there.
Your cranks are NJS square tapered. Standard Shimano taper.

My bet is something like this would work: http://cgi.ebay.com.sg/SHIMANO-BOTTO...mZ200302176719

I don't know what 'K-type' is.

Maybe this helps: http://www.sheldonbrown.com/bbtaper.html