You could buy universal ignition switch( $15.00), 2 reds are hot side,
brown acc 1(radio), orange acc 2(wipers,defrost), pink ign(coil),
purple(maybe yellow) starter. These are all ~10 gauge(thick) at steering
column running upto the key, you could snag them under the dash. You could
do the other way, toggle switch and push button for start but would have to
be very high current switches (30 amp min) without using relays,
better(cheaper) to use universal key switch. If your desperate to start you
only have to power up pink(ign) and power up starter(purp) to crank over.
Remember the thick red wires are hot all the time so you should have
the battery off when handling those wires, if you short them you'll probably
blow a fuseable link somewhere.
There might also be a way to access the ign switch thats bolted to the
steering column, I think a rod from the key switch activates the ign switch,
not sure if you can grab that rod under there or not.....Rico