I think I have the ultimate battery disconnect grin (used for security mainly). It's a Cole-hersee 24200 I think? solenoid. It's a latching solenoid, so you hit the pwr/gnd contacts momentarily and it switches on, hit it again and it switches off (using no power while not switching). You can trigger it w/ a remote, small switch somewhere, etc.

'53 Chevy truck 1/2 ton