You need a 200A relay (to act as a isolator while vehicle is off.) Minimum of 3 fuses. And a bit of wire.
Take the 200A relay; wire 85 to ground, 86 to ign, 87 to the Starter B+ and the 30 to the back bats. Then fuse w/in 12" of both front to rear and rear to front. Then of course between rB+...