Create directory “EFI” in your EFI partition (e.g. pendrive or hard drive)
Clone this repo and paste directiories “BOOT” and “OC” onto created directory
Download GenSMBIOS to generate unique SMBIOS information. Run it and select Generate SMBIOS, as model select iMacPro1,1.
Open config.plist with ProperTree and go to PlatformInfo > Generic. Set MLB (Board Serial), SystemSerialNumber (Serial) and SystemUUID (SmUUID) to generated values.
Boot it!
Post install
Ethernet
Settings -> Network -> Ethernet -> Advenced -> Hardware: Set Configure from Automatically->Manually Then set Speed to 1000baseT, click ok and apply.