Obviously knowing the origin or history of the engine helps... Knowing what kind of heads are OR were on the engine gives you some clues but most importantly pull out the freeze plugs (which you will do anyway) and check the gaps between the cyls, you can use drill bit shanks to get an idea of the gap (like a feeler gauge)...
Read here and go see what you have: http://www.jalopyjournal.com/forum/a.../t-639277.html
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