Originally Posted by cletis
Exception to the rule: 1955 GMCs with 6 cylinder were 6V in both series.
Big 1955 Blue Chip GMC trucks, 550-650 series "big trucks" were standard 12v. It is interesting to note that models 100-410 GMC V-8s were 12v, with some of the larger models having optional two/dual 12-v batteries.