I have answered my own question by the obvious, but tedious process of removing 64-bit versions and installing 32-bit. Exlink does work with Excel 2013 32-bit version, but not 64-bit (at least in my experience).
In general, it seems best to avoid 64-bit software if it has any external dependencies. The switch to 64-bit occurs more slowly than most other upgrades. Microsoft's advice for Office is clear: stay with 32-bit if you have no explicit need for larger data capacity.