I just read this thread and it remind me about my solution 4 years ago which is still working today. After a lot of trials after the head gasket was blown due to too high coolant temperature after purchasing the more effective radiator I just had to reduce the radiator surface. It was the only way to get arranged with the logic of the Ford coolant system.

Here is what I did then.
https://www.talkmorgan.com/ubbthrea...the-cooling-water-temperature#Post713083

'14 4/4 graphite grey