Installing NVIDIA GeForce GT 120 in x4 PCIe slot?

Greetings,

I'm not at all well versed in IT, so I am trying to find any information regarding whether or not I can install my NVIDIA GeForce GT 120 card into the #3 (x4) PCIe slot on my MacPro. Since I have read one could install 4 of these, taking up all the slots, then it must work in that regard, but I want to know if it will work as the only graphics card in that slot? I can't seem to find any information on what this card needs, other than what apple states, "PCIe 2.0 slot."

I am running a 8x video card, and I am also trying to spec out an 8 channel RAID. If I understand this right, I would need both of my x16 slots for these two, so can I run the NVIDIA GeForce GT 120 in the x4 slot? I only run one 2048x1152 23" display off of this graphics card. If it does work, what kind of limitations will I have?

Thanks.