Good question, forgot bout that. With mine, I had to keep the old relay up front for that. Kind of a P.I.T.A. and seems redundant. Plus you have wires running all the way back and front just to start the car.
The main thing that the Ford solenoid does is kill the big wire to the starter when it's not being used. If you run the wire inside the car, you kinda want the solenoid for that reason. If the wire is outside the cabin maybe it's less of an issue.
I got a lot of the ideas here from talking with the guy at Mad Electrical. Took a long time to understand and execute everything I ended up doing but again, once I figured it out, it all became clear to why things need to be set up this way.
The thing that makes wiring a cutoff switch with an alternator more difficult than it has to be is NHRA's rule that the switch has to turn off the positive side of the circuit rather than the ground side.
