Only thing I've seen is the small sketch Ron Cobb did showing Dark Star with gear. As I recall, it was a Greg Jein creation and while maybe it was based on some Ron Cobb stuff, I doubt it had any detailed blueprints made. At least there was a three view, which formed the basis of the damage schematic Talby looked at in the film.
As for a Studio Scale Dark Star, I've never seen one. But, there should still be a Dark Star Bomb build somebody did here a couple years ago (an SS build, using as many of the original kit parts as possible). I suppose maybe the Dark Star is scaled to that, but it would be a BIG model if that were the case. So I have a feeling the open bomb bay was a large section model, unless of course Greg Jein really did make the ship that big. I've never seen a shopping list for kitbash bits used either.