It is good news that you have a G30742-402 revision. This means that you don't have the PSU power on problem of the earlier revision of the DZ68BC.
The CPU power connection needs 2 * 4 PIN connectors. Your PSU (according to the screenshot of the sticker on the link in your initial post) has 2 12V outputs that can provide 17 A: it seems one for the 4 PIN CPU power and one for the 6 PCIe power (the picture of the wires and connectors is not very clear).
My proposal is to use an PCIe 6 to ATX 4 power adapter like:
(this link is just an example, I assume that many shops sell these things)
and connect this 12V power line additional to the current 4 pin power connector.
On my PSU I have two 4 pin connectors that could be connected to each other to create a 8 pin connector. This is however just a convenience.
Tip: If your still on BIOS 0028 I would be careful or even not upgrade to a 003X BIOS revision. A lot of BIOS issues have been reported in combination with sandy bridge CPUs (just search this forum)