You can actually run 2 solenoids if you'd like, 1 standard power-energizing type to run the starting circuit and 1 grounding type to run the power feeds. You'll have 3 wires running up front - 1 heavy-gauge, maybe 1/0ga or 2/0ga to the starter and 1 medium gauge, maybe an 8ga to a standoff to join up with the feeds and alternator output and 1 circuit-breaker protected 14ga wire to your battery cut-off switch. The starting solenoid's "S" terminal would be energized by the ignition switches "S" post and the power feed solenoids "on" terminal energized by the battery cutoff switch which needs to be no more than a toggle switch (hidden if you want to use it as a form of anti-theft protection. Add a Ford-style EFI pendulum switch to that feed solenoid ground wire and you can add the protection of automatically cutting off power in case of an accident.