the bottom line is, you need the input devices (IPD) board from an Air, unless the keyboard connector is a direct fit which i doubt. The power for the backlight has to come from somewhere, and the macbook may not have the extra "pins" to provide that power.
edit: i'm sure people wondered if it was possible to switch keyboards from a regular sized powerbook (backlit keyboard) to a 12" sized powerbook (which does not have a backlit keyboard). From what i remember from looking at all the spares we have in a box, the keyboard cables were different. hope this helps!
and then even if you get the IPD board from an Air, you'll probably run into problems connecting that into the macbook's logic board.