There is no separate 64-bit version of Chromedriver. The version available at https://sites.google.com/a/chromium.org/chromedriver/downloads works on both 32 and 64-bit Windows, against either 32-or 64-bit Chrome.
This was confirmed in the Chromedriver issue tracker: https://bugs.chromium.org/p/chromedriver/issues/detail?id=1797#c1
Yes, Chromedriver works on 64-bit Windows and against 64-bit Chrome successfully.
I came here while searching for the answer to if it works on 64-bit Chrome following the announcement that from version 58 Chrome will default to 64-bit on Windows provided certain conditions are met:
In order to improve stability, performance, and security, users who are currently on 32-bit version of Chrome, and 64-bit Windows with 4GB or more of memory and auto-update enabled will be automatically migrated to 64-bit Chrome during this update. 32-bit Chrome will still be available via the Chrome download page.
~ Answered on 2017-05-05 10:05:49