Pinout question: Is this just a PCIe x8 slot in a proprietary card

PCIe x8 to x16 extension cable - ADT-Link pcie 8x slot PCI Express Riser Card x8 to x16 Left Slot Adapter for 1U Servers pcie 40 in 30 slot A PCIe slot that supports a PCIe x8 card also supports a PCIe x4 or x2 card All slots support PCIe cards of up to 75 W The power of a PCIe

pcie 4 m2 in pcie 3 slot if the slot is open like that, you should be good to go if it's not open, you could a) use another riser to adapt the x8 to x16, or b)