I believe the Blue Sea part number was 9012.
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It's a fine solenoid for the job. They rated it 250 amps continuous, 500 amps for 10 seconds and 2,000 amps in-rush using 1/0 AWG cable.
When you're thinking about how to use it remember that it's not a charger. It's intention was to close when the engine is running and open when the engine isn't running, thus isolating the house battery from the starting one. When the batteries are connected it'll be the alternator charging both. When they are isolated you'd need to connect a charger to the house battery, if you want.
It is controlled using a simple switch, which could be a panel switch or you could use something like an ignition hot or voltage sense like they use on newer units (which have the voltage sensing built-in, which this does not appear to have).