#4.81
57-64 Ballest Resistor non HP
57-64 Except HP
63-64 Corvette 2nd Design Except Spec. HP & FI
65-67 Corvette except T- Ignition

#4.81A
5-6-7 Ballest Resistor HP
56-64 8 Cyl. with HP
55-62 Corvette with 12 volt
63 Corvette with & without Spec. HP & FI