Peter,

Probably "High Energy Ignition". Try a Google search on "ingition coil HEI" and you will get a lot of information. It seems like they mate accompany an "HEI Distributor" GM cars seem to use them. They have a higher voltage output than conventional coils and will probably fry your electronics. It appears that if you just avoid any coil with HEI in the name you will be OK. Most manufacturers seem to have both HEI and normal versions of their coils.

John