Either a high amp switch at the clutch pedal & route the 10 gauge starter solenoid purple wire that comes out of the fuse box back into the cabin, through the switch & out to the starter
OR a relay under the dash that just interrupts the purple wire & use 12V low amp wire to the relay to turn it on.
I don't have a clutch switch on my 2+2. I should, but no tech dept at a track has ever asked/cared.