Hi
This might help you or maybe not.
https://www.fordbarn.com/forum/showthread.php?t=290142
If you are dropping 6 Volts at 4 amps it is 24 Watts which would require a decent sized wire wound resistor and a heat sink . I think Ford used Nichrome wire wound on a ceramic former in those resistors as seen in your pic, the same wire as used in the old electric bar heaters, the resistance increases as the wire heats up. I can see a cover over the resistor in your pic, this is to shield fingers from the hot resistor. Where would you find and buy a Lynx part like that ?
The other issue is some of those Ford ignition coils were rated at 4.5 Volts not 6 volts.
You could use a solid state device to drop the Voltage down but they are rather prone to voltage spikes that destroy them .
https://www.ebay.com.au/itm/20427330...Bk9SR9y3oP3bYQ