Should be possible. A while back, we used some internal-only tools to flash a Raptor ECU ROM onto an '18 3.5 EB F150 to do some testing for parts development. Obviously it didn't run right because boost control is way off, plus various different physical parts on the engine, compression differences, etc, but we were able to get the data that we needed AND the truck ran. If your friend was to install a Raptor/'19+ Limited 3.5HO engine in the truck, and then was able to get the Raptor or Limited ROM flashed to the ECU, then the swap should work. Would probably want to do the Limited ROM due to differences with the Raptor's drive mode switching button configuration, although that's just a suspicion of mine and the Raptor ROM may work. Don't have an idea of whether or not the non-HO wiring harness would be 100% plug and play with the HO engine. Shouldn't have any issues running without the IC fans though.