I was able to find several similar questions asked and answered, but none of the answers or exact conditions applied to my situation.
This is an alternative to Ondrej's answer.
We just made the modification for our Release configuration in the project file (csproj) and set the SDK path to the x64 version:
... ... ... On C:\Program Files (x86)\Microsoft SDKs\Windows\v8.1A\bin\NETFX 4.5.1 Tools\x64