If you have JBridge, you can load 32 bit plugins into x64 Forte. However, although its a good product it complicates the setup and creates more uncertainty when something goes wrong. Typically if you go to 64-bit plugins, I'd recommend you should probably just go to 64-bit plugins too.
If the plugins are the same DLL name and plugin ID, the same plugin CLSID would be generated and it should just work. If the plugin DLL Name is different it may require a rack edit or adaptation to replace plugin identifiers in the rack file.
One workaround around this is to use jbridged plugins (even though the host is already 32bit), because jbridge runs the plugin in a separate process with a separate memory allocation.