It's relative to what system you are using. Electronic and HEI systems require at least an 8mm carbon type wire. Wire core is not recommended for these systems. A good 7mm carbon type wire would work on your year truck with the stock points distributor.
Probably $35 to $50 at most auto parts stores.
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