I don't think that you can use two Core i7 980Xs in a dual-socket motherboard, they're for single socket boards only. Otherwise you may only be able to use one CPU in the motherboard at any given time.
i7 CPUs only have 1 QPI which allows it to talk to the chipset. You need 2 QPIs so the CPU can talk to another CPU and to the chipset. So no, you can't use 2 980Xs in a motherboard.
Xeon 5500 (quad-core) or Xeon 5600 (hex-core) is what you'd need.
There is no board that will use two I7's you have to use xeons to do dual CPU system.
I think it's more correct to say that i7s cannot be used in multi-CPU systems (the lack of 2nd QPI as stated above), but it all equates to the same thing.