OER Parts offers a wide selection of Coils for your 1966 GMC 3500. OER Parts offers 1966 GMC 3500 OE Quality Ignition Coil, 1966 GMC 3500 Replacement Ignition Coil Premium Quality, 1966 GMC 3500 HEI Ignition Coils, 1966 GMC 3500 Chrome Ignition Coils, 1966 GMC 3500 Zinc Plated Ignition Coil Bracket, 1966 GMC 3500 Ignition Coil Resistor, and 1966 GMC 3500 Chrome Ignition Coil Bracket & Chrome Coil Cover.