76 midget coil ballast?

I have a 76 midget I recently acquired and am wondering what the coil ballast looks like? This car has been pieced together with mostly 1500 parts but the distributor is a D25 from an earlier model and I can't find a picture of the coil ballast in any manuals. I've never had a car with a coil ballast before but I'm installing a Pertronix set up and it says to attach one of the wires to the battery side of the ballast. Can anyone tell me what to look for? Thanks!