Although I'd be fine with a 2di number for the US-70 corridor I would think it would be better to save a 2di number for a longer multi-state route (man if only they could figure out a way to get I-30 from Little Rock to New Bern, but I digress into fictional territory, lol).
I would think that an odd 3di would be fine for the corridor, which would be a spur off of a major 2di anyway. As someone else had stated, 340 is available in NC and would be perfect for this corridor.
Man, and to think, it could have been I-40 had things gone differently back in the 60's and 70's.