I would like to use the right-Alt key (Alt Gr) as ⌥ key. These are modifier keys right of the spacebar on MS 4000 Keyboard:
. I currently have the Application key
mapped as ⌥, but Alt Gr would be less clumsy.
Update (or, failed attempt with KeyRemap4MacBook)
Microsoft keyboard drivers give these settings:

If one disables the 1st setting (Swap Windows and Alt keys), then the ⌥ key is next to the spacebar (on both sides, as in Windows). Now, one should be able to switch ⌥ and ⌘ on the left side (and keep the right ⌥ as is) in KeyRemap4MacBook using these settings:
Command_L to Option_LOption_L to Command_L
Alas, the _L settings also affect the right side (_R settings), that is, _L settings swap ⌥ and ⌘ on the right side as well! Am I doing something horribly wrong or how does one solve this in KeyRemap4MacBook?