The 30-378 with a custom chamber would be the way I would go. I would look around and decide what is the heaviest VLD bullet that I would want to shoot and have the throat cut to fit that. Maybe something in the 240 grain range would be a good choice. I would check the bearing surface on the big Accubond and the big SMK and make sure the throat is good for both.
Depending on whether this is a walk around gun or a sit on a rock and shoot a mile gun, I would get as much barrel lenght as I could tolerate.
The Smokin Fur Rifle Club