Precision 7865 U.2 support?

I currently have a 7865 with 2 SATA flexbays, and I'm looking at potentially swapping them the PCIE+SATA flexbays, or at least the upper PCIE-capable one.

Does anyone have any idea if the PCIE flexbay options for the 7865 also supports u.2 drives, or only m.2?

Also, any idea of the correct SKU/CRU number (USA or preferably Canada numbers if they're different) needed for said swap? I found the Dell instruction videos to swap in the PCIE+SATA flexbay unit or the upper PCIE flexbay, but they don't give the part numbers in those or in the service manual.