Montana, Trump's doing well:

Pseudo poll https://www.isidewith.com/2016-republican-primary-poll/801555698/9333326

And it's open primary which usually helps http://www.openprimaries.org/states_montana

Montana is winner take all http://www.thegreenpapers.com/P16/MT-R

South Dakota:

Pseudo poll https://www.isidewith.com/poll/801555698/9333341

SD is closed primary and that "poll" was weird, so I can't say how that will go http://www.openprimaries.org/states_south_dakota

SD is winner take all http://www.thegreenpapers.com/P16/SD-R

West Virginia:

Like others, a recent and reliable poll hasn't been taken, but it has this again https://www.isidewith.com/2016-republican-primary-poll/801555698/9333348

It seems like 22/34 of WV's delegates will go to the winner http://www.thegreenpapers.com/P16/WV-R

I think his odds are good there. He swept the South http://graphics.wsj.com/elections/2016/all-primary-caucus-results-2016/

Nebraska:

Again, no reliable polls, here's the best I could do https://www.isidewith.com/2016-republican-primary-poll/801555698/9333327

Looking at the map above: NE is in the area of Kansas and Iowa, which Cruz won- perhaps the Midwest likes him. Why, I have no idea.

If Trump can take Montana, South Dakota, and West Virginia then he can afford to lose Nebraska. None of them have good recent polls, though, so it's anyone's guess how that goes. As for the other three states, which are proportional, he should take roughly his national average. Having won AZ and NV, it's realistic to think he'll do well enough in NM, but I don't think anyone has any idea how he does in the Northwest.