With some care to your choices,
GW Ogre heads work on Mantic Ogre bodies. Mostly because of the Johnny Bravo proportions of the Mantic ones. You still need to choose carefully, though. Mantic ones won't work on the
GW Bodies though (at least not to my own aesthetic preferences). I do agree on the
GW Orc arms working well with Mantic bodies, as well.
https://azazelx.wordpress.com/2015/02/20/mantic-ogre-shooters-units-3-and-4-2013-2015-a-year-on-2/
I've only used them on unit leader heads so far. (just the two above, as I've only painted 12 mantic ogres so far). My issue is I actively dislike most of the Mantic Ogre heads anyway, but even with the 3? 4? 6? you get, I wanted more variety. I've got a few other
GW heads selected in a little baggie to be used for more Mantic Ogre units down the line.