The reality is that the Panteras were delivered new with the 192° themostat from Ford.
The only upgrade needed was to change out the original 4 blade cooling fans to the eight blade ones.
These cars were tested by Ford in Arizona heat and by the '74 model, everything was fine.
I use the 180° thermostat and pressure bleed the cooling system with a hand pump. You can hear the system gurrgling as the air bubbles get pushed out.
If you start to mess with this system, you are attempting to re-engineer it and if you think that you are smarter then the Ford engineers are, be my guest but here's the thing, you aren't.
The largest reason they overheat is 1) the '71 cars system design needed help. It wasn't fully developed. 2) people do not understand how to get the air out of the cooling system and what that means.
You need to use a pressure system like the one to test the pressure cap sealing to do it. It is actually very simple and people are still reading tips and procedures posted 30 years ago on the internet that are incorrect and misleading.