Would adding these work?

Have some 7950s i used to use laying about. Doubt i could run both but would it be possible to run both a 1070 and a 7950 in the same rig using risers or do they have to be the same brand+ would 750w be enough?
I have a 750 w evga gold power supply
i5 6600k
Z170M MORTAR motherboard
thanks