If I am understanding correctly:
1. Get the normal PC / Snoopy69 EFI and modify it to suit with SMBIOS, serials, etc. as per the norm for the past few years. Overall recommendation is (I'm asking here...) iMacPro1.1 now, or MacPro7,1? I think I've seen both.
2. Then, once that's all settled and the machine is bootable and works well, in order to get Wifi working, run OCLP vLatest (as of today, 1.2.1), targeting that machine's SMBIOS (there's a setting in OCLP for same machine while you're building the EFI modifications), allow OCLP to update your boot EFI (which targets ...err...the boot EFI), and then allow OCLP to update your root patches (which targets the OS partition). Reboot, and WiFi should work.
Is that all that's required? Is that middle step (modifying the EFI) required, or has that part essentially already done with the existing EFI that is provided?