Powering a graphics card in a Mac Pro 2008

I'm looking to update from the stock graphics card in my my Mac Pro 3,1 (2008). The logic board only has two 6-pin ATX connectors, and the card I'm looking at (a GeForce GTX 760) requires one 6-pin and one 8-pin ATX connector. From my research the power supply should be able to handle it, as I don't have any other PCI devices. There are 6-pin to 8-pin ATX adapters available, but I'm not sure the tracks on the logic board would be rated for the higher power, and may burn out. I do, however have a spare molex 4-pin power connector for an IDE disk drive. What is the rated power for one of these type connectors, and is there any way to use that, or a combination of that and the other 6-pin ATX connector to provide enough power to the card?

Thanks!

Please see this thread

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The Mac Pro has a special low-profile connector on the motherboard, so you need a cable like this or this_. Make sure the cable you get specifically says it is for the Mac Pro, there are many different choices and not all cables will work.

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