Original? 6 volt. Chevrolet went to 12 volt in 1955 with the advent of the best dam little engine ever produced and yes, Tork drag raced one in 55 & 56...
Reason I asked.....on that show I mentioned, Billie Biscoe was showing off the first car he ever restored. A 39 Chevy coupe with, according to him, “period correct parts”.....and sitting on the passenger side firewall was a 12 volt battery, big as day!!!