Switch Radeon 5770 in Mac pro 5,1 to PC GTX 680

I have heard that a Evga GTX 680 PC graphics card could be used in a Mac 5,1 mid 2010 without flashing it ?
What else would I need, don't want to shell out $$ for a Mac card if I don't have to.
Maybe have to sell the GTX 680  if incompatible ?
Thankz in advance
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http://www.barefeats.com/gpuss.html
Quoting article:
"The GTX 780 with 6GB GDDR5 video memory is only slightly slower than the GTX 780 Ti and TITAN Black but costs much less.
The other factor in naming it the 'sweet spot' has to do with power. The GTX 780 6GB runs fine on the dual PCIe internal power cables -- as does the GTX 680 and Radeon HD 7950."
"Though most of the attention is on the new 2013 Mac Pro. we continue to explore ways to 'pump up' the legacy Mac Pro towers. One of our favorite upgrade paths is the graphics processing unit aka GPU. We recently tested the GeForce GTX 780 with 6G of GDDR5 video memory (courtesy of MacVidCards). It just may be the 'sweet spot.' We'll explain after you peruse the graphs."