What ignition system do you have?
OEM Prestolite CD system.
Belt driven distributor Magna Power I system or converted to regular battery auto system with distributor?
Magna Power I .... Champion L20V
Prestolite..... Champion UL18V
Regular auto system with points distributor.....Champion L82C.
Magna Power and Prestolite need surface gap plugs, auto style with battery driven distributor with point need regular plugs with a bent electrode.