questions on push button ignition/

It would be simplest if you upgrade to HEI ignition, with no ballast resistor. Wire the toggle switch so it connects +12V power to the IGN and ACC circuits. I think these are marked on the starter switch. If not, go by the wire colors. You can find wiring diagrams for many cars by a FABO search (need a diagram anyway).

The push-button will connect +12 V to the "start" wire, which is yellow in most cars. This shouldn't change your existing relay or neutral safety switch.