I’ve personally seen a lack of a clutch safety switch go really wrong... thankfully nobody got seriously hurt... picture someone in your garage... maybe not knowing manual transmissions... or knowing only modern manual transmissions just trying to help you by reaching into the car and turning the key to see if the new starter works.
So, I rigged a clutch safety switch by tapping into the starter solenoid ignition (key turn to ‘start’) wire. The starter solenoid wire was clipped and in between I installed a $9 Yamaha vintage motorcycle spring-loaded brake light switch for the clutch pedal side. I also fabbed a simple bracket and anchored it through an existing hole in the clutch/brake pedal assembly mounting hardware. Then it was just a matter of cutting a spring to the correct size and watching my indicator light for a completed circuit as a depressed the clutch pedal ()
Also, I drilled a new hole in the firewall and installed a grommet for th new switch wires.
Yeah... I probably could have installed a 1970 starter relay that had a clutch safety switch terminal, but I wanted to do my own thing.