As referenced on this post: http://www.gmatpill.com/practice-questi ... orrection/
"Would take" = the period from 1860 to 60 years from that - so that would be 1860 looking forward til 1920ish
You would only use "took" if you were from the perspective of some future date (like today's present) and you looked back at 1860 and say that it took 60 years. But in that case, you would have to differentiate the distinct time of the "birthing" of the book and use "had been born". You need to do this to show which of the 2 past events happened first. The dictionary was born first, and then it as completed. So "it had been born"..and then "it was completed" is what we want. So you have two options: (1) would take......was born
"would take more than 60 years to complete, the Oxford English Dictionary was
or (2) took...had been born..
""took more than 60 years to complete, the Oxford English Dictionary has been born"
Hope that helps.
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