calvin200001 - I was having the same problem as the original poster. After installing Logic Studio 8, I was seeing "Logic Pro: Plug-in 'Hybrid Mor' not available".
Thanks for the tip above! It solved the problem without me having re-install anything from the Logic Studio 8 disks. I used my Logic 7.2 disk 2 (Content), installed to the Desktop, then copied to the empty folders as you described. In order to copy to the empty folders, I had to right-click, Get Info, and change ownership and write-permissions of the target (empty Hybrid Morph and Hybrid Basic) folders. Once I copied the right files, I set the ownership back to "system" and permissions back to "Read-only".
Thanks for sleuthing for the shortcut way to do it!
There's no time like the present. Literally.