Seems to me our '87 Mk III had one 8D on the starboard side (i.e., under the lower helm) and that doubled as start and house. And then we had a genset start battery, probably Group 24-ish or 27-ish back under the cockpit with the generator.
We had no bow thruster, no electric windlass, and inverters hadn't been invented yet.
Were I doing it today, I suspect I wouldn't bother to isolate house from engine start. Instead I think I'd just cram about six 6V golf cart batteries where the 8D lived (assuming I could make all those fit) and call it good. There should be plenty of cranking amps to start the relatively small diesel... and there's always the genset and charger as a back-up.
And never having to lift an 8D again... priceless.