There appear to be four main leads coming from the center and top of the ballast.
First blush would be that each of those represents the + and the - .
The lower magnet(?) appears to be closest to the source. Probably why the harness, as it were, seems to come from there.
To be honest. Not loving the condition. Any of these wires dry rotting? Make sure to wrap anything that looks abused by time with electrical tape.
@Uncle_Al what do you think?
pic of the other end of the wires?
pics a little further from the scene of the crime too.