Why would you want to do that anyway? The styles are very similar, yet each one is crafted to go with the rest of the body for that particular model. Switching the heads would be pointless hassle, in my opinion.
If you still really want to do it, though, You'd have to rename the texture for one of the models to RTAD (provided you haven't got millenias weapons installed) and then use kimera to set a different texture ID for the head part