Apart from the lug the water channels are different, the 4wd consisting of a series of holes, whereas the 2wd has long slits, other differences as said, if in doubt just get 4wd cams, as these fit the 2wd head with the addition of a spacer, so I would imagine no one would make a 2wd cam now just the 4wd type and offer spacers to suit 2wd be a lot cheaper tooling wise.
tabetha