There might not be a need for resistor plugs.
Do you have a radio? 6v/12?
What plugs are you using now? Do they produce interference with other devices (cell phones, maybe)?

The original was AC 44-5 plug

http://www.sparkplug-crossreference.com/convert/AC_DELCO/44-5
http://www.sparkplug-crossreference.com/convert/CHAMP_PN/RH8C