Yah cadillac had a two engine monstrosity too
Ok, so Frank and Carlos hint at some good points, lets make the following additional assumptions for simplicity:
It is rear wheel drive (i.e. ladder bars and chain/sprocket) so you don't have to worry 'bout torque steering or complicated steering geometry and drivetrains.
It is liquid cooled with sufficient valving so you can keep either non-running engine warm with waste heat from the other.
You shouldn't need a differential.