55.2 through 59 trucks used a ceramic type ballast resistor as did cars of that era. The resistance "wire" was introduced in the early 60's.
Your 64 truck came with a resistance wire unless someone changed it out for some type of HEI system that requires a full 12 volts to operate.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine