short update - I successfully transplanted a 7970m from a P150EM into my P150HM.
The 7970m was v1.1 - not v1.2 - even it had large capacitors which were re-soldered by Clevo.
It did NOT work with the Clevo vBios attached in this thread, it only worked partially until I installed the latest AMD driver for it, resulting in a bluescreen.
I then tried different vBIOS-versions, dead-flashing the card twice (I have an USB programmer, so no problem at all), and in the end I flashed an old DELL vBIOS v015.017.000.001.042717 onto the card, from techpowerup (will upload the flashed bios later...):
https://www.techpowerup.com/vgabios...&version=&interface=&memType=&memSize=&since=
With this vBIOS, everything works now - driver installation, no bluescreens, GPU fan only gets loud on load, runs stable (benchmarks & gaming - Wolfenstein II for hours).