I have many new voltage regulators that came with a collection of parts. Basic, standard looking black, rectangle, delco style regulators. They all have different numbers on the backs. On the inside the all look the same. How do I tell if for 6 or 12 volts? And perhaps what trucks they go with.

Numbers include.
8AA
3KD
1HD
9CB
2LB
7FA

Thanks.

Trombones Totem Poles And Old Trucks!