451 overheating, even when moving

canajien said
Here's the test results after 20 mins of idling and fans on

Lower hose next to the rad 195

Upper hose next to the thermostat 205

Thermostat housing 212

Coolant in the top of the rad 198

Any air has to be purged by now, time to try a different fan, unless the previous owner was running race coolant, we test drove for nearly an hour before I bought it and there was no indication that overheating would be an issue.

Amazon has the mechanical fan in stock, and it can be here tomorrow...

The headers were all pretty much around 950 to 1000

I apologize, I missed the upper/lower rad temps .
You appear to be getting only 15* of temp drop thru your rad, that might be enuff for a garden tractor . lol
If you take the temp gun, and shoot all across the rad, about halfway down, you will likely find cool/cold areas, those are plugged tubes not passing hot coolant.
The bigger/more cold areas, the bigger the problem .
Before temp guns, I'd run my knuckles across the front of the rad, searching for cold.
Cheers