Do you have your VSTs in a separate folder for 32 bit and a folder for 64 bit? For example: "C:\VST 32" and "C:\VST 64".
Then set the path in Reaper's preferences listing the 64 bit folder
after the 32 bit folder. Reaper should now use the 64 bit version of your VST, when the 32 bit and 64 bit VST are named the same.
Hope this helped.