In the current 3.07.0.1 plugin release, there isn't a proper version for the H16.5.
In any case, the plugin code has been updated and it is ready to work with the new Houdini 16.5 version. I'll include the first H16.5 plugin build in the next release, early next week, that is going to include also some of the new Octane 3.08 features.
Computer Graphics Software Developer
Octane plugin development and support: LightWave and Houdini