Ignition Kill Switch Wiring Location?

[ConchZ]

Hi, I've got my dash off and have fixed my crack. Before I put it back in, I'd like to install this keyless entry, car alarm system I bought. It has a relay for a starter disconnect. I've been hunting through posts for ideas on how to wire this thing up without hacking my wiring harness up too much. The car is a 1973.

All I need to do is place the relay inline with either the starter solenoid, or the coil wire. I believe it would be easier to install by breaking into either the BW or GW wire on the tach. Since the dash is out, I have easy access to install this little relay close to the tach for a nice clean installation. I also think that cutting power to the coil this way would make it nearly impossible to get the car started, vs simply cutting the starter's power. Nobody would ever figure out why the car wouldn't run, unless they pulled out the tach.

Does it matter if I use the BW or GW wire? Any advice before I start playing electrician? I do have a Crane Fireball 700 ignition and coil, but if I remember right it still gets its power via a circuit passing through the tach.

Thanks.