That comment about one wire to ammeter and other to ground IS WRONG AS RAIN. The ammeter has hot battery voltage so do NOTTTTTTTT connect either terminal of it to ground.
1) The Load (NOT battery/starter) side of ammeter supplies hot battery voltage to the BAT input terminal on an Ignition switch. If it had a 4 termnal VR with an L terminal, the VR"s L would feed the voltage to the switches input instead of the ammeter
2) The Ignition switches other (hot when ON) terminal wires down to the input (NOT to distributor) small coil terminal
3) The coils other (NOT from IGN switch) terminal wires to the lil side terminal on a Delco distributor.
If you had a Wico XB distributor, then the Ignition switches IGN output wires to the side input terminal on the Wico XB distributor
Its like the diagram I posted EXCEPT the ignition switches IGN output wires to the coil instead of to any Wico XB distributor.
Dont make this any harder, if its a Delco distributor its almost like the diagram, just wire the IGN switches output (HOT when ON) to the coils lil - terminal and its lil + wires to the Delco SIMPLE AS THAT
Id polarize the genny before start up just to be safe