Carb size for mild 440

Good morning everyone,

I am a little out of my element here.

A friend of mine has a 67 Satellite with a motorhome 440. The engine is stock internally with the exception of a Hughes Whiplash cam, performer intake manifold. Car has 3.23 gears, tall rear tires, and stock exhaust manifolds. The car is used as a driver, road trip machine. The owner is looking at putting an new Edelbrock AVS2 carb on it. Although it is a 440 cubic inch engine I was thinking perhaps a 650 might fit the bill. I do not want to steer him in the wrong direction, am I wrong, does he need an 800? Ultimate performance is not the idea here, drivability and utility are key. Thanks guys.