ignition noise in the radio is from arcing in the ignition system. usually from spark plug wires . the wires on old vehicles is in need of new loom and proper hold downs .higher than normal resistance of the plug wires causes this also or open in the wire silicon core ..
the spark plugs spark in the engine this is not causing this because the spark is in a enclosed metal bore. then the other reasons usually are arcing ignition coil/bad distributor bearing/cap and rotor. if the rotor wobbles then the distributor needs replacing...
the hood also if not grounded well and it does happen because of rust allows this electrical noise to get into the antenna of the radio.. placing a ground wire attached to the hood helps reduce this .. but if those plug wires are arcing then that will not completely fix it.
make sure the plug wires you get have about 3K ohms resistance or less.