Build Issues in BimlStudio

When trying to build in BimlStudio, but recently upgraded to 64-bit from 32-bit as I was having memory and performance issues.

I do not see the BIML Engine file. It, seemingly, does not exist in the correct location.
    
Not sure what I might have missed while trying to recreate the project in 64-bit?

If the 32 bit file is present in the program files (x86) folder then you just need to add the actual path to the 32 bit file in the settings.

If the file is not present, you need to install both 32 and 64 bit versions of BimlStudio.

Also, if you have all prereqs and SQL Server installed, or if your project configuration doesn’t use SSIS script components, you can instead test to build out in 64 bit mode.
            
In the build and deploy ribbon UI tab, choose 64 bit instead of 32 bit in the drop-down, and retest the build.