Though all these maps make sence, I don't think that South Dakota would go Democratic. It only went Democratic in 1964 due to Goldwater scaring South Dakota farmers. He said he would end farming substidies.
I take your point on that... however in a situation where a popular incumbent was running for re-election I think many places would come into play for JFK as they did for Reagan and Clinton... with the his populist polices in relation to agriculture that would have helped farmers and rural communities as well as more general positives such as his strength on nation security and the economic "good times" I think this region would have been very competitive in the event of a Kennedy v Rockefeller race...but in the end of the northern west and far west i reckon that Kennedy would in the end have only pulled out wins in WA thanks to the growing urban population and perhaps in SD because of the strong democratic party machine there at the time...ultimately I think the answer to your question is that in a race like this a lot of places would come into play that would in a 50/50 race of the time would have gone GOP...