Chilkat has a .NET 2.0 DLL available for 64-bit Windows systems (x64). It can be downloaded from this URL:
http://www.chilkatsoft.com/d2/ChilkatDotNet2_x64.zip
Your .NET 2.0 x64 builds should reference "ChilaktDotNet2_x64.dll" whereas your Win32 builds should reference "ChilkatDotNet2.dll".
All of the Chilkat .NET 2.0 components are available for 64-bit Windows.
If you have trouble, please send email to Matt Fausey (support@chilkatsoft.com).