Thank you wildwillow, both Einsteiniac and I have mentioned that we tried the HDEF patch from the frist page, update #2 and it does not work...
OMG jesusthecaffeine - thank you so much - your link to a post worked perfectly to resolve my black screen after apple logo with the web drivers for a NVIDIA GTX970 card. That's why I love posting here - not sure how I would've ever found that.
Following the instructions from that thread, I changed my iMac 17,1 board to none (it was DB15BD556843C820):
Issues I still have:
1) I have done the audio patch from earlier in the thread to my clover plist, but Toleda's auto patching script "audio_cloverALC-110_v1.0j.command" errors with:
OK to patch
Error: no IOReg/HDEF; BIOS/audio/disabled or ACPI problem
No system files were changed
(Attachment showing IOReg and System Preferences shows my line outs and microphone outs)
2) only 8 GB RAM instead of 16 GB
3) Broadcom bluetooth not working
Thanks!