I'll add a little bit to the list:

On Missouri streams, I've done well with streamers....and sometimes have slayed (slew?) them with black stone fly nymphs. Maybe they look close enough to helgramites.
From the rivers you mentioned, you should do well. I would also look into the Jack's Fork River, the lower Current River, and the Little Piney.

I've spent all of my life in Missouri and I'd be glad to give you any help I can. In 2010, I was planning a trip to Yellowstone and looked for tips and ideas and Walt, you were most helpful to me while I was planning my trip. PM me for any specifics or questions you might have.

Brian