About the importance of this grounding strap... I had an engine replaced in a non Ford (
) in 2018 and the installer failed to reconnect the engine to firewall grounding strap. The result was that when the engine was cold, it fired right up. When it was hot... you could not get it to fire up.
This happened about the third time outside a NAPA store... and one of the employees saw me with hood up and ventured out. He called his dad who had been an electrical engineer at GM and got him on the phone. Right away he said to check the grounding strap. It all had to do with more resistance as the wires and electrical system heats up... and the resulting flow of electrons being reduced. Same principal I understand as the purpose of the ballast resistor between the Ignition switch on my '35 Ford and the Coil. So that when the ballast resistor is cold, I'll get the full 6.7 volts to my coil and as it heats up then is reduced to I recall between 3 and 4 volts to the coil.
Anyhow... just things I have learned from advice and 'hard knocks'