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 are used with an "HEI Distributor" and have a higher voltage output than conventional coils. They will probably fry your new 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