Technical Shoebox push button start wiring?

So im doing the 12v conversion on my 50, totally stock electrically and so far everything has been pretty straight forward but i've hit a roadblock.

I want to use the original ignition switch with the push ****on start switch, originally these car were 6v + ground so the push ****on has one lead going in to it, when you push the ****on the circuit is now grounded and the car starts, right?

to keep this switch would i just reconnect the lead at the key switch to the wire that goes to the shunt behind the temp gauge? is that the ground?

 

I've officially confused the **** out of myself

 

wait, if i keep the original starter solenoid i wouldn't have to change anything right?

Sorry i'm thinking out loud

 

Yes. You won't have to change anything. Route the wires exactly the same. The starter solenoid will also handle 12 volts just fine.

 

okay thanks, i needed a sanity check i guess

 

To use the starter ****on, just change the ****on switch to a two post. One lead from the battery post on the solenoid, the other to the 'start' post (one of the small ones on the 12 volt solenoid)
If you want to retain the single post ****on (6 volt ****on switch) run the wire to a 50 amp relay, which has the power (30) shunted to the 'work' terminal, so it is 'energized'. Run the grounding starter wire to the 'ground' on relay; pushing the ****on completes the circuit by providing the ground.

Anybody that disputes use of relays here should equally lament the use of 12 volts.
Or just do as PeteJoe says, (if you aren't already vested with 12 volt solenoid, etc.)